I'm pretty optimistic. On one hand, Disney takes very good care of characters -- look at what they've done with their Marvel acquisition. On the other, you have an entire generation of fans in charge of making sequels of the movies they love. This is different from when the original authors revisited some of these things (remember Indy IV?)
For what it's worth, Kevin Smith implied in a podcast that he saw it a few weeks ago (he's NDAd), and very clearly said this is the movie we were all waiting for. And not just because of the nostalgia factor or fan service, but because it's a great, entertaining movie that will bring you back to what you felt when you were a kid.
I, for one, find solace in Kathleen Kennedy reassuring people on multiple occasions that there is no Jar Jar and there are no midichlorians discussed or shown. I'm OK if they drop a reference at the First Order committing genocide by using Starkiller base to destroy the entire solar system where Naboo sits and wiping out all Gungans from existence. And open with another full-scale test and vaporize all Ewoks while going at it. I mean, how else are we going to believe these new villains are meaner than The Empire?
OK, I geeked out.