I prefer original recipe, myself. And none of that special edition chipotle sauce crap, either!
See, I think you can have their descendants, but they're distant descendants. Like, 3-4 generations down the road, or more. Initially maybe you don't make it absolutely clear, but eventually you reveal the backstory and explain that, no, the main character is actually descended of Luke himself (or Leia).
I'd prefer to not see the OT characters at all -- just because I don't think there's an effective way to do it without it ending up cheesy -- but I absolutely agree that a Sith resurgence is the wrong way to go. I have my own idea of how to handle the Dark Side thing or Jedi going bad, but honestly, it wouldn't really fit the good/evil dichotomy that runs through Star Wars. It'd be far more "shades of grey" (no not THAT shades of grey, you pervs) and more about well-meaning people who take bad means to reach a good end, instead of moustache-twisting villains like the Emperor in the PT. ("UNLIMITED POWAAAAHH!!!! NYAHAHAHAHAHAHAHA!!!")
The way I see it, power has the ability to corrupt all by itself. You don't NEED a Sith organization. You can just have a Jedi who sort of espouses SOME of what Anakin talks about in AOTC and Vader references in ESB: "We will bring ORDER to this galaxy and END chaos." That also touches on some of the tenets of balance in the OT and PT -- that when you're out of balance, you invite discord, and balance need not be numerical balance (5000 jedi vs 2 sith) but rather balance within oneself and living in harmony with your environment instead of fighting for control of it.
To my way of thinking, a better representation of the Dark Side is the desire to IMPOSE control, to bend things to your will, and the willingness to use whatever means necessary to do that, even in the pursuit of a noble end. And ultimately, the most effective villains, I think, are those who come from noble beginnings -- the fallen hero -- rather than the psychotic. Someone who goes from "Lawful Good" to "Lawful Evil" basically. Chaotic Evil is just boring.
I wouldn't count on it. We aren't the demographic that buys toys. Or rather, if we're buying toys, we're buying them for our kids, nieces, nephews, etc. (Yes, I know plenty collect toys, but for a real merchandising market, we ain't the demographic sweet spot.)