Should the Sith return in the sequel trilogy?

True, which would open it up for more than just two.

My thoughts too.
Its kinda like Yin and Yang. One must balance the other.

e- typo

You have to remember that in the history of Star Wars, the Sith have 'died out' and come back several times. This should be no different. So Palpatine/Sidious and Vader are gone. That doesn't mean there can't be another Sith, or even a fallen Jedi who becomes a Sith, to bring conflict and chaos to Episode VII.

And I think that with the next movie being an original story, all the EU stories after RoTJ become irrelevant. (I do hope they bring Mara Jade into it, however, as she was the single greatest thing the EU gave us.)

Very true. She was named in the top 20 Star Wars characters. The only from the EU and just infront of Stormtroopers in poplularity.

Screw the sith. Grand Admiral Thrawn.

I don't care that Ep. 7 is an original story. I don't care if it has Sith in it or not. My main wishes are:
#1: Bring Back Luke, Leia, Han, and now they just confirmed BDW is coming back as Lando!
#2: While they dont have to adapt an EU story, don't throw away over 30 years of hard work by the authors and over 30 years of new characters we've grown to know and love. Keep the Skywalker/Solo families like they are in the books (Luke, Mara, Ben / Han, Leia, Jacen, Jaina, Anakin), and don't contradict any existing stories, and I'll be happy.

And I loved the Vong. Just saying.

HK Army anyone? I am pretty sure they are the only force that can push down the full Jedi Order at this time.