I am on H1B came to US in Feb 2008, wife joined me in Mar 2008. My daughter born on July, now my wife and kid are planning to leave to India in Dec 4th. My wife has her SSN.(she got that when she came to US in 2005)
Will I get the IT return benefits of filiing jointly also the stimulus payments?

You can file joint return as residents. If your daughter was born in the U.S. you will get her SSN and can claim her as dependent. You will also get child tax credit of $1000 and stimulus rebate (if your income does not exceed a limit).
You must report your worldwide income for 2008.