Yes.

Monolith Soft is owned by Nintendo now, while Namco Bandai owns the rights to Xenosaga. This essentially sends the series into the same copyright black hole that the Chrono series suffered. Until this changes, I doubt we'll see another Xenosaga game any time soon. If we do, I doubt it will be anything resembling the first three games considering the creative team is signed with another company.

Which I think is a shame. I'm actually playing Xenosaga III for the first time, and quite enjoying it.