I think he's going to find out through someone else.

I honestly think someone else might tell him, or he might figure it out himself(despite the fact that he's a dummy...)

Finding out from someone is definitely a possibility but I want Quinn to tell him, and while i am not sure if its going to be in the next episode, I am pretty certain that the truth will be revealed pretty soon!

I really think that Puck will tell him.

considering if you've seen wheels I agree with _lina_ I think Puck will tell end up telling him so he can have anything to do with HIS baby girl.