Monolith Soft has not finished working on the Xenoblade series yet. Or, at least, he wishes it to be so. This is revealed by a message attached to the Japanese release of the official Xenoblade Chronicles 2 soundtrack.
This, in general, the translation of its contents: «we want to continue with the numbered chapters of Xenoblade. […] We want to publish a third Xenoblade, and a second X. »

Among other options, Monolith also wants to continue working on completely original video games. The news tells us that it is already doing, considering that we are talking about work in progress for a new project.

Source. Reddit