How could he come back?

NIW I485 pending, I am the applicant and my hu*****and is dependent. He went back to China six months ago. He wants to wait until the green card approved and I mail it to him then he will come back. I worried that even if it is approved since he left US more than 6 months ago, he can not come back with his green card. what if mine is approved first and he want to come back, what kind of visa he should get? I am on H1 and he is on H4 visa now. I am so confused and thanks for any suggestions.