Maybe temporarily? Such as he gets called to Celestia's side for a time in order to assist her with something, likely a royal summit involving the Dragons. And he winds up staying with Celestia in Canterlot for... like... five episodes or something. Or he gets sent to the Dragon Lands to help strengthen relations with the dragons and he's there until the finale or something, at which point he comes back as a slightly larger dragon, more pony sized or something. Like he's grown up after his time among the dragons.
Not unless there is some kind of disaster that causes a major falling out between them, like a political crisis or some other major drama, but nothing that I can see them putting into the show with its rating.
Twilight is practically Spike's Foster mother at this point, and plus, having a dragon around is a strategic asset, so I'd doubt that Celestia would let him leave permanently. It's not like he's under any other power besides Equestria.