It has confirmed that the EU is not being factored in to the sequel trilogy.
Really, even Thrawn trilogy has some silly stuff I'd want gone, and it's handling of the Clone Wars and even the force doesn't really match up that well with the movies (Joruus mind controlling thousands). If you aren't going to do the movies based on the Thrawn trilogy, then including their plot in canon just makes things harder.
Now, it wouldn't surprise me if you saw some winks, like a blue admiral, but it won't be the same story.
Actually Thrawn can be in it, because they can borrow anything from the Old EU they like. It would just be in the context of a completely different story and continutiy.
So the fact that Thrawn was around in the EU only 5 years after ROTJ has zero effect on whether he can appear in Ep.7 thirty years after ROTJ.
All that being said, I doubt he will be in it. Abrams and Kasdan probably wanted to come up with their own Original Villain(s).