I have already sent in my 4th quarter ET on my Required Min Dist. There is a possibility that the sale of my second home will settle in Dec 2015 as it will be capital gains, do I need to send in additional est. taxes or can I wait and take care of it when I file taxes for 2015?

If you file by 31 January 2016, then a second estimated tax payment for the IRS is NOT needed.

However, assuming you DO itemize, you WILL want to make another 4th quarter estimated tax payment to the STATE, since such a payment is normally tax deductible if, made before 31 December 2015.

Estimated taxes for income made in the 4th quarter are due to be paid by January 15, 2016. So yes - you should send in a 2nd 4th quarter estimated tax payment by then, and not wait till your tax return filing in April 2016.

After reading ebaines post, I see that my answer may have been less than clear.

To clarify, the requirement to file a second 4th quarter estimated tax is NOT needed if your annual 2014 tax return is filed by 31 January 2016 and all taxes are paid in full at that time.