This could certainly be his creative way of straightforwardly teasing what’s in store for his character when the series airs, although again, the new show’s proposed direction and general plot description look to be set during a later time.
Disney likely won’t confirm things one way or the other until production moves along a bit further.
Ben Mendelsohn’s quote seems to imply he wasn’t aware of the series’ goings-on, and that he has not been approached about appearing in the Disney+ Rogue One prequel project.