IS LUKE REALLY DEAD, CAN HE RETURN BACK ON THE NEXT SEQUEL?

Yes, and yes!

There is a theory going around the internet that he didn't become one with the force aka force ghost. Some are saying he teleported to a different planet. Even Rian Johnson and Mark Hamill are kind of in on the theory as well from one interview I read. I think Rian Johnson said something like his robotic/metal hand went with. If he became one with the force, his robotic/metal hand would've just dropped. And when we see Anakin return as a force ghost, he doesn't seem to have any robotic/metal limbs or even a burnt body. So that means Luke will have his real hand back if he were to become a ghost. But what debunks this theory is that Luke's clothes remained behind and blew away. If he teleported, they should've went with. Unless he is doing some teleportation like in The Terminator movies where they end up at their destination naked. But Rian Johnson isn't really part of Episode 9 so just because he is in on the theory doesn't mean he's hinting to something that will happen in Episode 9. Plus after all the time wasted on who Snoke theories and theories on Rey's parents, I'm not going to waste my time believing this theory. I don't even know if I want to bother theorizing or speculating once trailers to Episode 9 start being released. I'll probably just watch the trailers and then go back to my life like I never watched the trailers.

With Star Wars you never know. Heck, I've heard folks say that snoke isn't really dead.


:-)

They opened up Force powers to include anything and everything. If they wanted to have Luke just will himself back into existence they could. I bet you for sure we see a Force Ghost possess somebody sooner or later.