I understand it's a lack of motivation, especially after doing the same thing for four years, and you want to try new things. So I guess the game is already "finished," right?
Even so, I think you have a very large community (although it may be quiet) for that game, and I sincerely believe you could give it a well-deserved send-off, even if it's just a DLC that has something users really want.
Anyway, I respect your decision and wish you the best. I hope all your projects turn out as good as or better than this game.
Thanks for everything :)