I'm not at all surprised he was able to come in and be productive, I just didn't think with the contract to Foster, that he'd get the opportunity until next year. He's not going to be sent back down this year, and I think it's pretty safe to say he'll be a full time Oiler next year as well.
In a perfect world, the Oilers would find someone more proven to man the top pairing with Whitney and Petry would slide into Foster's spot on the 3rd pair with Smid, leaving the 2nd pairing of Peckham/Gilbert (which has actually been the top pair even before Whitney got hurt as far as matchups go) in tact. But the Oilers threw Gilbert to the wolves in his first full season after showing promise as a callup the year before, and they don't look at all interested in actually improving the team, so I think it's more likely they pair Whitney with Petry and keep the rest of the pairings as they are. Next year's defense will probably look about the same as this year's defense which was arguably the worst in the league.