I don't see Bryan getting taken out of the main event scene after WM if he drops the title to Sheamus. Right now, he's the top heel on SD, and I think a draft would bring him to RAW to eventually face a champion CM Punk, maybe play off their indy history a little.
I'm rooting for Daniel Bryan to win at Wrestlemania. If he loses, I can respect that he's had a good run, and I like Sheamus. But I'm worried that, as consistently as he's delivered in the top heel role, if his run as champion is ended this soon, WWE may mistake his heat as just being related to AJ, and Bryan could get Mark Mero'ed.
This idea might not be popular, but I'd say Bryan should be kept on Smackdown, and he should hold his belt for a long time, longer than even Punk holds his. Punk is at the stage where he doesn't need to be champion to be definitely over. But the longer Bryan holds that title, the more it could really make him, and he in turn could help make that belt. If the WWE Heavyweight Title is the "real" top title, and the World Title is the "B-title", then surely that's the belt you can feel free to experiment with, right?
Here's what I'd do. Have Bryan retain against Sheamus, and keep it on him, for months, and months. I could see WWE thinking Summerslam would be long enough, but I'd honestly be fine with the reign lasting until NEXT Mania, and I'll explain why. A year-plus world title reign is pretty much unheard of in WWE in this day and age. He's hated now, but when you factor in the boredom and frustration people felt when JBL held the title for ages, his heel heat would reach a whole other level. Heighten that with cheap wins: DQs, countouts, cheating, and cheap little small package victories out of nowhere. Have him feud with the top guys like Orton, and come out of it victorious. Eventually, it goes beyond people feeling sick of Bryan being the champ. If WWE can weather that period, it then becomes something more special: where there's a breathless anticipation for someone FINALLY beating him, which gives his every defense even more drama. If WWE takes the time to build someone they think can be a top babyface for Smackdown, have them win the Royal Rumble, challenge Daniel Bryan, and then you FINALLY, after years, have a Smackdown title match that feels like it could be as big a deal as the Raw title match, because the prospect of Daniel Bryan finally dropping the belt becomes a draw in itself. And because he's held the belt so long, when he puts over this emerging babyface on the grandest stage of them all, he puts them over huge.
Yes, I'm aware it's pretty much pipe-dream territory, and I can't blame WWE or be disappointed if they wouldn't do something like this. I'm aware of the flaws: what about the other heels on Smackdown's roster, where do they go in this environment? One thing I'd say is that Cody Rhodes needs to go to Raw at the next draft and be CM Punk's new nemesis. But setting aside fanboy wish-fulfillment, practically a storyline like this would have benefits, for Bryan and the title. It gives some prestige to what's too often considered the "B-title", makes that belt feel like something special and important. And even if Bryan doesn't hold the title again after that, he's pretty much made for life as the guy who had the title reign for the ages.