H-4/I-539 Transfer Query From Employer A to B

[SKRS]

Hi, I am transferring my H1B from employer A  (earlier I was with employer X) to B but my dependents H4 approval is still pending from USCIS for employer A so employer B suggested that let start transfer my H1B first in Premium then will initiate transfer for my H4  to employer B after H1B approved for employer B and H4 approved for employer A.

I am thinking what if my employer A revoke my H1B(approved)/H4(still pending approval) after my H1B transfer approved and joined into employer B. My question is how to proceed my H4 transfer to employer B? Does anyone has the similar scenario? Please suggest.