What's next for Barrett? I expect him to still be featured very prominantly. He was a part of the "Tribute to the Troops" Main Event tag team match. The announcers made a point of pushing how tough he was repeatedly during the match after he had been "buried" under chairs at TLC. So basically, it was 3 days off of TV for Barrett, before he made his return in a Main Event. Id say thats pretty prominent myself.
As for where he's headed, I think contrary to popular belief, Undertaker's return will not lead to another feud with Kane. Rather, Undertaker will appear to feud with the people, and most noteably, person, who buried him alive. That would be Nexus, and Wade Barrett specifically. Barrett specifically discussed that there was a reason for why they buried the Undertaker, which David Otunga re-iterated. I expect that to be a feud down the line, possibly at Wrestlemania if Taker's healthy.
Right now, Barrett will be re-grouping. I don't believe that the end of Nexus will be at the hands of John Cena. I believe that Nexus will combust from within. Barrett will attemptt to re-assert his control over Nexus, and they will realize he's abandoned them at every turn. The in-fighting within the group will lead to a feud heading into the Rumble, with Barrett ultimately emerging victorious and cementing his place as a top heel. He'll be one of the last to go in the Rumble, and will be a part of The Raw Elimination Chamber.
He won't win either, but he'll stay on the cusp of the main event scene until a relevant feud comes along, perhaps with Randy Orton, if Undertaker isn't healthy. Nexus and Barrett were ultimately responsible for softening Orton up that allowed Miz to take the WWE Championship from Orton. Miz and Orton likely had their blow-off match on Smackdown, so id expect in the here and now for Orton to attempt to exact revenge on those who cost him the title. Wade Barrett lead the charge, so he will likely be Orton's target. I expect a Barrett/Orton feud, which we got a taste of for the title. However, it was very secondary to the Cena/Nexus angle, so no proper Barrett/Orton feud was done. I expect once Barrett re-groups and exerts control or domination over Nexus that his next feud will be with Randy Orton.