Well the banking division is gone forever, there is almost no way that a federal court would declare the sale of those banking assets void. Not only undermining the FDIC but potentially causing another widespread panic. The hit to JPM's stock would be very bad, and possibly cause a bank run even though JPM would be capitialized even without Wamu's bank. I mean lets be honest they only paid $2B.
Now judge in this country would reverse that and undue all the work thats been done already by JPM. So yes the bank is gone.
However the possibility still does exist for:
1. JPM and/or the FDIC to be forced by the court to pay the difference between what JPM paid and what the actual value of those assets minus the liabilities which JPM also took.
2. Settlement where the value of such would most certainly be less than a court judgment of the same action.
Either way, WAMU stock still presents a pretty unique opportunity for willing investors. Great risk, potential for great reward. The only question is ... are you willing to take that risk? I know I am/have.