I am on H-1B visa more than 6 years. I also have I-140 approved. However my H-1B is under renewal process. I do have 'receipt of notice' but not approval notice yet. Looking at the waiting time I don't think I will get H-1B approval along with renewed I-94 before May 26th 2015. I need to file EAD for my wife on 26th May.
See clip from Attorney Rajiv S. Khanna's conference call video that addresses this question.
https://youtu.be/y6RtaKhuoIY
FAQ Transcript:
The answer is probably yes. But if you want to be even more circumspect you could even premium you’re H-1B. I mean if you are that concerned about it. Lot of these things have not been clarified but we do except them to issue a clarification before May 26th. Until then the practical approach I believe is you could apply for H-4 EAD while the H-1 extension is pending and you could, based upon the approved I-140 ask for the H-4 EAD but in the meantime you can also premium your H-1.