There was always supposed to be a Listen Without Prejudice Volume 2 and the Trojan Souls duets album. A number of tracks for LWP Vol 2 including Too Funky were put on the Red Hot and Dance charity album.
Also George did a number of new tracks for his Greatest Hits collections so some of these tracks may have been used there.
George also said writing Patience album was hard work so if he'd had decent stuff in the vaults it doesn't appear to have been used there.
He may have a few unreleased tracks but no treasure trove of unreleased albums. Also if he didn't feel the material was to his liking to be released then, I don't think it will be released now out of respect for George.