J1-Waiver and GC through Spouse

[Buckeye12]

Hello,

My wife is doing her J1-waiver and little less than two more years are remaining, meanwhile, I am becoming US citizen in next couple of months.

My question is, should I sponsor my wife for GC once six months remaining for her finishing J1-waiver?

I know one guy told me that he had sponsor his wife while six months remaining for her wife's waiver and it is legally allowed (he is a born US citizen though). But I want to make sure that I could do that, too.

Any suggestion or comments, please.

Thanks in advance.