Source.As noted, Daniel Bryan will now face Roman Reigns in the main event of WWE's Fast Lane pay-per-view with the winner facing Brock Lesnar at WrestleMania 31 for the WWE World Heavyweight Title. Original plans for Fast Lane had Roman Reigns defeating a top heel, possibly Big Show, and Bryan being used to put Bray Wyatt over to keep him strong for The Undertaker.
Regarding booking for Bryan, WWE wanted to put him into a feud with Sheamus for WrestleMania 31 but his opponent was switched to Dolph Ziggler after Bryan reportedly requested the change. It's possible that Bryan vs. Ziggler still happens.
For what it's worth, people handling the actual promotion of WrestleMania 31 were still under the impression that Reigns vs. Lesnar will be the main event as of this week and in the promotional material, Reigns is to be the most heavily promoted, followed by Lesnar and John Cena. It's worth adding that WWE has not included Sting in any of the WrestleMania promotional material and since he's all but confirmed for the event, his involvement will be a major selling point so new material should be released soon.