ANN reports that the January issue of Animedia contained a quote from the production staff of Code Geass at Sunrise Studios:

"All of you have shown us much appreciation and made the DVDs as well as the CDs so popular. Really, we have been blessed with fervent fans…. Thank you very much. Like we have said before, [a major character development happened] but Geass cannot die. It just ended, but we think it would be nice if we can still do something more. In any case, when we can announce something, in the not-so-distant future…"

Whether an actual sequel, prequel, or simply a spinoff is unknown but definitely Sunrise is not going to stop milking the cash cow.