My reading of this whole catastrophe is that the certification of the B737MAX and the B737NG may now be thrown into question.
The FAA will undoubtedly approve "MCAS 2.0" in as quick a time as they consider respectable, but the evidence shows that there is such a degree of regulator capture that this will be hard to see as an objective evidence-based process.
Others, particularly CAAC and EASA, may not be so easily convinced. The Russian regulator would probably be onside with that judging by their actions a couple of years ago to attempt remove certification from the B737NG.
I think the Whistle blower testimony may impact what decision that the FAA is even able to make. I'll bet that both Boeing and the FAA are keen to just patch MCAS and move on.
However if they start getting expert whistle blower testimony that brings in to question the whole certification process of MCAS and the reasons for its existence the FAA will be out of options other than some sort of re certification process which is a whole new can of worms.