Takahashi stated that the "Xenoblade" title is more or less of a title Monolithsoft uses to indicate the game is headed by himself.
So I dunno. Even if the gameplay is drastically different, they'll probably stick by the "Xenoblade" title regardless.
Yeah, there's not a whole lot that connects the two games right now beyond terminology and general gameplay fundamentals, so there's no reason to ditch the IP as it's already rather flexible.