Sting should have defeated Triple H at Wrestlemania and THEN put Rollins over (albeit due to nefarious tactics) at either Summerslam or Night Of Champions. The way it is now, I don't see a good outcome for this match either way. Either Sting loses his second consecutive match (and his second straight battle to The Authority), or Rollins loses his title to a guy who's clearly just gonna end up being cashed in on by Sheamus not too long after (which will inevitably lead to Sheamus replacing Rollins as The Authority's chosen one, something I doubt too many people are dying to see.) And unlike some, I do see there being a reasonable chance of Sting winning. I think Vince probably got all the "WWE>WCW" stuff out of his system at Mania.
I'd probably bet on something like either Rollins getting himself counted out by running away with the title, or Bray Wyatt appearing out of nowhere and costing Sting the championship, since a lot of folks - myself included - are speculating that Sting might face Bray Wyatt at next year's Mania if the Taker match doesn't happen (which given the likelihood of a rubber match between Taker and Lesnar, it probably won't), and this could be the early set-up for it.