A little background on the situation first:
My husband and I (same-sex) have been together for 11 years this Thanksgiving, and married for half of that time. We started our relationship with the understanding of polyamory, but didn't feel ready to start dating until a little over a year ago.

We had a few bad experiences and decided to stop looking. Five weeks ago, though, we were feeling a little lonely and put up a Craigslist ad for a No-Strings-Attached sex partner. We got tons of replies, but one in particular stuck out. This guy turned out to be amazingly intelligent, funny, gorgeous... Everything you could want in a boyfriend. We asked him if he wanted to be friends as well, he agreed, and so we began to hang out. We've had a date night every week since. Sex has been a part of it, but only at the end of a very long night, and after which he stays the night and cuddles between us in bed.

It's only been a short time, but we've developed some pretty strong feelings for this guy. My husband never likes any of the guys we date, and even he is excited about this guy. It's to the point that not a moment goes by that wouldn't be made better by his presence. When he's not around, he comes up in conversation at least every hour. In a perfect world, he would move in so we could see him more often.

The question is... How do we go about moving this to the next phase? How long should we wait to tell him, without waiting so long he moves on to someone else? The biggest concern is HOW to tell him, without it being intimidating (two-on-one kind of thing).

He is an INTJ personality; a bit reserved and not the most expressive of emotions, so very hard to read.

Even though things are going good now you will learn more later, but the time to honestly express yourselves is NOW! You may not even like the guy next month, and eventually the lust will fade. At least communicate honestly not just your lust, but your concerns as well.

You should be honest with the guy, first, this is a change in the relationship, he may not be looking for that. He may just want fun sex, lots of men and women look for something extra at times, This was all you were asking or looking for, at first.

Next, there is not really a "next step" since this is not the agreement or what you were looking for.
This is an entire new staircase.

But he should know, so, he has a voice and discussion in it. He may find no interest in it, nor want a "next step"

I'm confused - you posted a while ago and said you were married to your WIFE, who you had known since you were 15, and SHE was a lesbian - what's the deal?

A little background on the situation first:
My husband and I (same-sex) have been together for 11 years this Thanksgiving, and married for half of that time. We started our relationship with the understanding of polyamory, but didn't feel ready to start dating until a little over a year ago.

We had a few bad experiences and decided to stop looking. Five weeks ago, though, we were feeling a little lonely and put up a Craigslist ad for a No-Strings-Attached sex partner. We got tons of replies, but one in particular stuck out. This guy turned out to be amazingly intelligent, funny, gorgeous... Everything you could want in a boyfriend. We asked him if he wanted to be friends as well, he agreed, and so we began to hang out. We've had a date night every week since. Sex has been a part of it, but only at the end of a very long night, and after which he stays the night and cuddles between us in bed.

It's only been a short time, but we've developed some pretty strong feelings for this guy. My husband never likes any of the guys we date, and even he is excited about this guy. It's to the point that not a moment goes by that wouldn't be made better by his presence. When he's not around, he comes up in conversation at least every hour. In a perfect world, he would move in so we could see him more often.

The question is... How do we go about moving this to the next phase? How long should we wait to tell him, without waiting so long he moves on to someone else? The biggest concern is HOW to tell him, without it being intimidating (two-on-one kind of thing).

He is an INTJ personality; a bit reserved and not the most expressive of emotions, so very hard to read.

I agree with aliseaodo. I, too, am confused. Just over a year ago you were here asking about how to start a relationship with a 19 year old while in an open marriage with your lesbian wife. (https://www.askmehelpdesk.com/relationships/straight-friend-768855.html) What is the true story?

Thanks to the first two replies for trying to be helpful. I definitely want to be honest with him, but I'm just not sure how we should approach things. Should we have him over for a nice dinner and after both sit him down and just lay it all out? Should we let him know that we have something to share so that he has some forwarding, or just spring it on him? Since he's shy and timid, should we do it through text so he has time to gather his thoughts before replying, or should we do it face-to-fcce and risk him feeling 'outnumbered and pressured'. Any tips on trigger words to avoid to how to phrase things, even?

Also, I'm not really sure how a post from a year ago matters, but my "wife" is in transition from female to male (FTM) and therefore now prefers male pronouns and descriptors. This new guy is fully aware of this and it's not important to the story.

Sorry you feel my request for clarification was not helpful - your post didn't make sense to me, that's why I asked. Last years post you had a lesbian wife, this year you mentioned a same sex husband. (Who is also having sex with this new male? Lesbian in transition to becoming a man, having sex with a male... that part still confuses me... I know you said you found this guy on Craigslist, but I'm going to ask - is he the same guy from last year?)
Anyway - whatever the details may actually be, it sounds like you're overthinking this whole thing. How about a straight forward 'we're really enjoying what we have with you, are you comfortable seeing us more?'

Part of the reason, it does matter, many of us, worry about wasting our time, on fake stories. Some people come here, every now and then, with more unusual stories and things that push the buttons of normal.

Ok, nothing much unuusal with gay marriage now a days, although there is a large portion of population that would get into a rant about gay marriage.

But you add, then a plural relationship, or basically a open life style, this is against most principles of even gay couples, who want only one partner.

So, we have people, we refer to as "trolls" who only come, to see if they can get a rant or some posters upset over a wild story.

I believe some may have suspected this, since your posts do not match up

You and your wife should put your heads together and come up with a plan. You have had experiences before with this kind of thing and surely have learned a few insights from past failures, and no doubt will learn more from THIS experience. Trolling for dates on any online social networks comes with risks and possible failures.

What's the hurry with this experiment? I suggest you take the risk and enjoy what you have while you have it, and see what happens. I don't think there is a set strategy for success in regards to any relationship endeavors. Life doesn't come with guarantees for anyone.