Anything is possible.
If you look at the evolution of gaming out there, there is a huge mobile market. Many people don't even have a PC any more. They use Android tablets, iPads, phones, or even watches. With VR headsets and virtual gaming gloves, the opportunity for complex interactions with a mobile device become nearly unlimited.
Have a look at this game I just found called Grow Stone Online:
3 Million user choices! Do RPG, Dungeon, Battle, PVP now! So addictive game
play.google.com
Sorry for advertising another game here, but at the moment it's technically not in competition with UO since it's a mobile game, right?
Anyway, the game-play is very basic, but the way they handle commands, access your pack, allow for resource gathering, crafting, and even PVP, it starts to resemble a slim version of something like an Ultima game - or maybe Final Fantasy - but anyway, the point is that it shows that this type of game-play is definitely possible.
This doesn't mean that the ServUO code could get ported easily to a mobile platform, but the basic ideas could. If someone started small, and grew from there, continually releasing new content, it would most definitely be doable. As much as most of us don't like Pay to Win, most of the mobile game development out there tends to use that mechanic in the form of in-app purchases, but as with any shard here, if you limit the purchases to deco, character beautification, titles, etc. then you could still generate the revenue necessary to "keep the lights on" without letting it drift into Pay to Win.