I don't think a win, a title or a call from Mercedes to replace a retiring Hamilton is going to help.
This feels like the cumulative stresses of disappointment in what F1 is becoming. He's questioning whether he wants to be part of a future that he appears not to understand... ...or want to understand. He keeps talking about lawyer's speech and literalism being an ever-increasing part of the sport, and this being very different from the sport he grew up with. That's not the speech of someone likely to become re-adjusted to F1's pattern. Also, he got married last week, which could indicate an increased desire for commitment. I don't think the FIA is in any position to commit to him, if commitment means giving up the literalism that allows it to regulate.
Sebastian has a sense of honour, doesn't seem depressed, and I don't think he'll break his Ferrari contract or use loopholes to leave them early. But I expect him to be gone at the end of 2020, and for Charles to have become team leader before that point.
(I would hate to think what Sebastian would have made of the Formula E race yesterday. There was a restart order issued, and about a quarter of the grid marched to the official and declared he was totally wrong, quite loudly. One, I think, only got away without a fine because his swear was in Portuguese and masked by three other drivers trying to speak at the same time as him. It turned out everyone in the conversation was wrong, but the official was more right than the drivers... Had Sebastian been in that group, I get the feeling he'd have been among the miniature mob.
The kicker was that a couple of the other drivers were looking on, and appeared to be amused at the drivers' antics.)