I think what the WWE will do is have him retire as champion at 'Mania and they'll hold a tournament after 'Mania and crown a winner. Normally I'd say crown a winner at the next PPV (Backlash) but this is WWE, they won't necessarily do that.
That however, is what I think WWE would do judging by their mind. What I'd like is a shock. I love shocks in wrestling and I mean a real shock not just WWE's pissy little ones, WWE's 'WOW!' ones. We haven't had one in a while.
You can do a lot of things with the JBL character as he's very wealthy and money can make anything happen.. anything.