I am on H1B and my H1B validity is till 06/2019 and hence my wife's H4 validity is also till 06/2019.
Lets say, a new employer files for my H1B transfer and my wife's H4, and they get approved with validity till 12/2020. Can my wife use this new H4 to extend her EAD (considering all the requirements are met like I-140 etc.), even before I join the new employer?

I will appreciate an early response.