Jeff Dee posted a short note in the Ultima Dragons Facebook group earlier this month, in which he gave some details on an Ultima spin-off that he came up with whilst working at Origin Systems:

While I was at Origin, I submitted a proposal for an Ultima spinoff (like Savage Empire and Martian Dreams). The idea was a space mission from medieval fantasy Britannia to its moons, to get more moonstone. It didn’t get picked up, but I thought you Dragons might be interested to hear about it

In response to some questions, he went on to explain his idea a bit more:

The details weren’t ever all worked out. My personal preference would have been to link it back to the kind of spaceflight which occurred in Ultima 1.

It’s not much to go on, but the concept itself sounds interesting enough. The idea to bring back some of the anachronistic space technology from Sosaria’s earliest days was an especially nice touch (but maybe I’m just saying that because it’s an idea I’ve had myself).