rickyson33
"The Baby"
Doesn't completely rule out the possibility of "legacy" being tied with Xenoblade, especially if you tie the concept that XCX has left its own legacy for a sequel to exist. But admittedly, it would possibly be a stretch.
If "Legacy" is in fact tied to Monolith Soft, it's either a brand new game/IP, that Zelda title I mentioned earlier with you playing as Zelda (Zelda leaving behind her legacy as the Princess of Hyrule), or possibly a sequel/remastering of XCX.
All are possibilities really.
it could also just be a new Xenoblade subseries
I see no reason why a Xenoblade 4 or whatever name they want to give that couldn't have an entirely different codename than 1-3, I actually find it doubtful that it wouldn't considering they publicly labeled that as it's own thing and called it the "Klaus Saga"