It looks like whatever work David DiGilio accomplished is now being handed off to a new scribe for another go around. Jesse Wigutow has been hired as the new writer for the sequel to Tron: Legacy and will continue the development of the script. I suppose it's possible he could be starting from scratch, seeing as there has never really been any sort of details released regarding plot, but it's just as likely he's writing another draft of whatever DiGilio turned in.
Joseph Kosinski is still set to direct, and while unconfirmed, I'm sure we'll be seeing Garrett Hedlund, Olivia Wilde and Jeff Bridges again as well. Kasinski is working on his film Oblivion at the moment, but once finished I'm sure Disney we'll wrangle him in to begin production on Tron 3 shortly afterward. Money doesn't make itself after-all!