AFAIK all of the Fantasy material was stored at the Iron Mountain facility after the Fantasy building was sold. Most reissues/box sets released after that had already been conceived at that point. I have no idea who the responsible people at Craft are - they now handle all reissues - and what their criteria are. The new finds of Vince Guaraldi recordings suggest there could be some unreleased Tjader material as well, especially from live dates, but who knows?
New finds in recent years were live recordings from other sources, like the double CDs on Acrobat and Elemental.