Luke PROMISED to troll Kylo forever. He PROMISED. "Strike me down and I will be with you forever," he said. And lo, Kylo stuck a lightsaber in him! Well, in his image. Close 'nuff!

So yes, there had better be some OBNOXIOUS JEDI GHOST action in the next film, or I will be miffed. ("Master Yoda, you have taught me many things. Including that being a ghost and poking the living with sticks is THE BEST."
"A hellion in my youth, was I! Wondered, you did, how I knew the dark side could dominate your destiny? Close, I came! Eeeh-heh-heh-heh!"
"...yup, it figures.")