This is just about the silliest thread ever, isn't it?
I guess it all depends on what the OP means by "signed." Signed, as in, agreed to be in the video game? Clearly. Signed, as in, anything more than that? That's a stretch. Signed, as in, agreed to wrestle? Hysterically unproven, baseless assumptions and unsubstantiated, wild speculation.
Signing on to be in the video game doesn't mean he's agreed to do any appearances for the WWE. Even if he's agreed to do appearances, autograph signings and such, for the WWE, that doesn't mean he's agreed to actually work for the WWE in any capacity. Even if he agreed to officially work for the WWE in some capacity, that doesn't mean he will ever actually appear on TV. He could take on any number of backstage roles, or do stuff with the kids in NXT. Even if he's agreed to appear on TV at some point, that doesn't mean he'll be making regular appearances. He could just show up to promote the video game, or do a one time guest host thing(probably not), or just appear at WM next year when he goes into the Hall Of Fame. And even if he's agreed to a full on screen role, that doesn't mean he's agreed to wrestle. He could be a manager, GM, commentator, etc. Do you see now how big of a leap it is to assume that he's going to wrestle just because he's going to be in the video game?
Clearly, Sting is currently on good terms with the WWE. He did the thing for Warrior and now he's agreed to be in the video game. That's awesome. But if I'm going to guess what this means for his future, the only thing I would put money on is that he doesn't go back to TNA. As for the question that Cole asked Triple H, clearly that's a good sign for anybody who does want Sting to wrestle, but they're promoting a video game and obviously the speculation about him officially signing with the WWE is a good thing for everybody involved. It just means that they have a positive relationship, and possibly that WWE is open to the idea of him being on screen.
Has he signed? Will he wrestle? I have no idea. It wouldn't surprise me in the least if he did. (Although the one thing I do know is that it WON'T be against The Undertaker, given that Undertaker has already wrestled his last match and retired.) But it's a stretch, to say the least, to think it's a given based on him paying tribute to the Ultimate Warrior and appearing in the video game.