Well here is the spoiler.
Yes, as long as there are clones, or bodies(like juicy little skywalkers/solos), the Emperor can keep coming back. The Emperor's Spirit will be destroyed if it possess a dying cripple jedi in a clockwork egg body.
The last of the Emperor's clones are destroyed by the combined efforts of Luke and Company, then by a feral Jax. Jax died being killed by the last of the Loyal Royal Guard. (Crimson Empire Series)