Takahashi will never get tired of Xeno, it's his lifework, and he'll complete it before he retires (he's getting old now). He has his own division at Monolith Soft to work on Xeno, and the rest of the Monolith Staff can work on other projects. Mostly working in 1st party Nintendo games, but we can expect some other game down from them the line alongside Xeno.
Takahashi is 59, you can maybe expect two or three more Xeno games if the next one comes by next year.