First - no way in hell do I see "STING" in the smoke.
There were advertisements on Youtube from the local area that were promoting that RAW show with the ad "the return of The Undertaker" and F4W reports that that's what the videos are for. I'd say that's who it is. But who's to say that's the only thing WWE is planning. Like someone else said, it was reported that WWE signed three deals before the Rumble and with the way Bischoff handled things on iMPACT, they seem pretty sure he isn't coming back there. Maybe WWE is promoting Taker's return like this publically but they also have Sting ready to go, knowing full well that those videos will create speculation. If I was a praying man, I'd pray that this is what Vince is doing, lol.
And if it were a one year deal, yeah there's some stuff I'd like to see Sting do. Losing to Taker is obvious to me because Sting is WCW and Taker can't lose to him in "his house," no way. There would be absolutely nothing to gain from it. After that, I wouldn't be opposed to Sting going over Kane and then, maybe getting his loss to Taker back at SummerSlam. Getting Sting some momentum back that way would be good leading into an angle with Cena, something like he took out the WWE's legend, can he take out the WWE's present? And I'd really like to see him finish up with Punk. I think Punk could play on Sting's past well and lead to some great promos between the two. And, if it'd be Sting's last match, it'd be a must for Punk to go over. Punk's a popular guy and he's over in WWE but that win would cement him there. And I don't think anyone would be opposed to it because Sting isn't a "WWE guy" while, in a way, Punk is.