Not many people got to work on RotS so it's people like these and Christian Simpson who got to work on it who will be worth collecting.
Some big name Star Wars Actors do nothing but go from one convention to the next for the last 30 years leaving Milllions of Autographs all over the world!
It's these rare Actors Autographs (e.g Revenge of the Sith people like this) that will be worth the money in the future because they may only try 1 or 2 conventions and not any more.
The ironic thing about it is, the bigger names who've been doing it charge more for their autographs too, yet it's more likely they'll be worth less in the future!
Another tip - Don't get them personalised for future valuation.