Id be interested to see what a Nolan version would look like , but other than him - how many fantasy directors are there with the credentials that come anywhere close to pulling this off ?
Pete Jackson ?
Spielberg ( who hasnt dont any decent in years ) ?
and then your left with a coin toss of an unkown or a Director whose films have all been medicore or unrelated at best.
Lucas at least had the advantage of doing a sci-fi film before star wars that was pretty good but I dont see any one else out there exactly lighting up the film world worth mentioning.
The best case scenario I can see is someone with a real passion for Star Wars ( like jackson did for LOR ) coming in and perhaps restoring some credibility and popularity but it will never approach the originals IMO unless its something right out of the ball park .