It makes sense that there would still be an ongoing fight with Imperial remnant forces (who aren't ready to just toss down their weapons because the rebels say so) after the destruction of the second Death Star, as they they try to maintain the Empire and retain control over sectors where they have a solid grasp. The Thrawn stuff would be silly, Imperial forces aren't ever going to answer to an alien, would make no sense at all, so it's good they are going with an original story line and not EU. The Empire has many competent officers that would be eager to crush any effort to fully re-establish the Republic.

There are lots of possibilities, and certainly Luke would be working on rebuilding the Jedi Order, and it would be cool if he appeared (but only if it's Hamill). :)