I had heard Garriott was working on a new game, but hadn't dug up anything at to this point. For those too lazy:
https://www.shroudoftheavatar.com/ Another of those crowd sourcing deals, though.... I feel like rolling my eyes because that has become so cliche, but then it's the greatest thing in software development, too, when it goes right.
It's not a spiritual successor to UO, it's a successor to the Ultima games and is still set in New Britannia. Looks like they've also pulled in Tracey Hickman to do a lot of the writing and lore stuff (for those not familiar, look up his books; most are pretty good to great).
Opinions expressed in this statement are the authors alone and in no way reflect on the game development values of the actual developers.