I don't think he'll leave, but I don't think it's anywhere near as impossible that he'd return to Cleveland as some of you seem to believe. Gilbert has since apologized for his rant (as has LeBron for The Decision) and LeBron's made no secret of the fact that he's been observing what's going on with the Cavaliers since his departure. He even gave a shoutout to Kyrie and a few of the other players on the team on Twitter a few months ago during one of their games. He's slowly but surely making amends with many people in Ohio, both in Akron and Cleveland.
I think he really appreciates what he has in Miami, but I also feel like he's still a bit remorseful about what he did and would love an opportunity to do right (in his eyes). As long as he feels like the organization is heading in the right direction by the end of the year, I definitely think he'll consider a return to Cleveland. Ultimately, I think he'll stay with Miami, but if he leaves, I only see him going to Cleveland - not LA, not Chicago, not NY, etc.