I could see Bryan's championship reign going a number of different ways. I think he'll lose it at Summerslam at the earliest and Survivor Series at the latest. I would prefer if he got a long reign, ala Bret Hart from '94 and Shawn Michaels from '96, both of whom held the championship from Wrestlemania to Survivor Series in those years. And they could easily stretch his championship reign out that long because Bryan doesn't exactly have a short list of opponents with whom he could square off with - Triple H (who he's obviously fighting at Extreme Rules), Randy Orton (he has a rematch clause in his contract, although the last thing I want to see is another Bryan/Orton match), Batista, Bray Wyatt, John Cena, and, of course, Brock Lesnar. Here's one way Bryan's championship reign could go:
Extreme Rules - Triple H
Payback - Randy Orton
Money In The Bank & Battleground - Batista
Summerslam - John Cena in a rematch from last year
Night Of Champions & Hell In A Cell - Bray Wyatt
Survivor Series - Brock Lesnar