If BC fully cooperates with the PW investigation, he will likely either be condemned or exonerated. If there’s gray area (e.g., the tweets were sent by his wife), the parties will likely negotiate a settlement and part ways.
If BC doesn’t fully cooperate, the Sixers will fire him and refuse to pay a cent. If BC sues, he’ll have to provide the Sixers pretty much everything through discovery that PW is asking for now. That information will likely either condemn him or exonerate him; if it’s somewhere in between, the parties will likely settle.
Not every investigation by a white-shoe law firm drags on for months; indeed, one of the reasons those firms command such exorbitant fees is because they can bring the necessary resources to bear to wrap up complex matters in a short period of time. It won’t take PW long to get to the bottom of this unless BC stonewalls them, and in that case, the Sixers will just fire him and deal with the ensuing lawsuit.