Vader, but how much Vader? I'm not expecting him to be the main character or even a secondary villain, but he can't just show up at the end like Luke does in TFA.
Anything over 15 minutes of screen time would be amazing.
People are smoking grade A Crack if they think the greatest villain to ever grace cinema won't show up in some form in this movie. He's currently on TV in a kids cartoon. Of course he'll show up in a war movie about stolen deathstar schematics that probably takes place weeks or days before the events of A New Hope. And you can count on Tarkin showing up too.
Yeah, the main bad guys are new Imperials and stormtroopers etc. But I could see Vader being used somewhat like like the shark in Jaws, only with even less screentime. Establish he's involved/giving orders in a scene with the main Imperial officer baddie. Then have him show up and wipe the floor with some of the key Rebels.
I thought it was confirmed a while back that Tarkin would be in it, as a digital re-creation of Peter Cushing.

I didn't even know there was a difference with the darth vader suits, all looks the same to me
Does anyone know if James Earl Jones will come back to do the voice?
Does anyone know if James Earl Jones will come back to do the voice?
Vader was such a prominant presence during the time between EP III and EP IV that not showing him in some capacity would seem very strange.