Even though there are "reports" of him possibly going back to TNA, in my honest opinion, that would be a mistake. Why? Because he has nothing to bring to TNA. He'll be lost in the shuffle of Fortune vs. Immortal, Angle-Jarret, Joe-Pope, it'll be a waste. Sure, it's a lighter schedule, but going to WWE would do wonders for Steve Borden.
He can be inducted into the Hall of Fame, and be known as one of the biggest star's to ever never wrestle for Vince McMahon.
He may also have his retirement match at WrestleMania, in the hometown of WCW, Atlanta Georgia. Many fans will order the PPV because of the nogastical feel and Sting will finish his career in front of 50,000 people and not 1000 people. He also could have one of the most epic storyline's with an "internet hoped," WrestleMania opponent, The Undertaker.
Plus, WWE is now PG (he didn’t want to sign before because it's was to edgy and raunchy and Sting's a born again Christian) and two of his friend's, Booker T and Kevin Nash, are back with the company, maybe he'll realized how warm they were both welcomed back and the crowd reactions were and the overall WCW feel early this year, maybe he'll want to have a match at WrestleMania to cap off his career.
Or he goes back to TNA for a year, gets lost in the Immortal-Fortune storyline, gets in a feud with however they put him with, and he retires next year in front of 1000 cast-members and 1 million viewers.
Anyway, if I was Sting, I would think twice before resigning with TNA. He's 52 year's old and is a legend in this business. Going to WWE this year or 2/21/11, or next year would be a great way to end his career. He can just sign a legend's contract, much like Bret Hart's contract, wrestle maybe, one match in a WWE ring, and be have his likeness and merchandise be used by WWE. Imagine, Sting on Smackdown vs. RAW 2012. Hell, atleast be inducted into the Hall of Fame.