H4 visa extension

[PankajD]

My wife is on H4 visa which is expiring on 30th Sept 2017 (and same I94 expiry date which is attached to I797) and my H1 is expiring in Feb 2018. We both have not traveled outside of the country after getting H1/H4 (Oct 2016). I was on L1 visa earlier.  

I have filed for an extension last week with my current employer but haven't received the receipt notice yet. I have got an offer from different employer now but h1 transfer initiation will take a couple of more weeks, I'm planning to move based on receipt number but worried about my wife status as I will have very little time get her H4 filled. As per my understanding, as long as I have receipt number before the expiry of the visa, we're ok. Thereafter, we can't move out of US until visa gets approved. But I'm not sure if I can get the H4 receipt number before 30th Sept from my new employer. Could there be any issue? Can I move based on my current employer receipt number (for H4)?