Keep this list in your "favorites" Mark.
http://www.surrounddiscography.com/quaddisc/quadpall.htm
Unless the artists/label orders a freshly minted 4.0 or 5.1 release (anniversary reissues, usually).....chances are pretty slim that they'll release those artists in multichannel.
It's Audio Fidelity's policy to ONLY release 'existing' quad/5.1 releases unless they change their tune (but it would involve a LOT more money to have them custom remixed for surround).
REALLY wish they'd re~release the botched Ten Years After "A Space In Time" 4.0 mix (reversed front/rear channels) as a hi res QUAD SACD!