We did get a little taste of that controlled, calmer, at peace Luke in ROTJ. (I also liked how he responded to Han's gratitude in the deleted sandstorm scene.) He certainly came out of his final duel with Vader a wiser person who knows now how not to let a foe push his buttons.
Mark has also had the chance to play other characters tempered by war since the OT, and I look forward to seeing Luke as a master.
I'd be willing to bet the first teaser we get has a shot of Mark taking his hood off ala Sir Alec in SW. And audiences will go crazy. ;)