What we are reading at the moment is based on Chelsea's briefings to the press, and the fact that they seem to be claiming that: (a) JT has agreed to stay if contract negotiations with the club can be concluded successfully; and (b) he is willing to hold those negotiations. If this is true, it doesn't remotely justify the level of certainty being expressed in various newspaper stories today. The fact that they'll offer him a new deal doesn't mean he'll agree it.
I believe that Chelsea have been briefing the media in this way for two reasons:
1. They do hope to persuade Terry, and genuinely think they have a good shot at doing so, to stay by making an offer which, though it won't get close to matching City's, will be enough to keep him at the club given his natural affinity with Chelsea; and
2. If he then doesn't stay, they can say, "Look, we entered into talks and offered him a big pay rise, would have made him the best paid player in the club's history, and yet still the mercenary b@stard has gone up there for the money," painting the club in a good light and Terry in a bad light in PR terms.
At the moment, the only person who knows what's the most likely thing to happen is John Terry himself. For reasons I won't go into again because I spent hours doing so last night, I believe that by going to City, his earnings in the next few years will see him trouser a sum that's greater than he'd earn at Chelsea by well into eight figures. I think the vast majority of people in his position would find that quite hard to turn down. That alone means we're still in with a chance, until Terry makes clear otherwise.
At the moment, no one on here, and no one at Chelsea or City other than Terry himself, really knows what he'll do. Maybe he'll stay. But at the moment, it's far from an inevitability.