Im sure the deal was only to make sure ITV keep broadcasting the formats of boths show, ie X and BGT. nothing else?
I thought he was still in a golden handcuffs deal with ITV but it appears that expired in December. I do still think he'll be on ours though even if just an impartial judge during the live shows, I think this is all just hype. I don't think Cheryl will be back though. Its probably the right time for her to move on anyway, the tide started to turn on her last year.
ITV will probably want Simon to prove X Factor can work without him as he did last year with BGT when he was "ill" and temporarily replaced with Louis.