SWG is gone, and I haven't played UO in a long time, so I don't know what it has become.
WoW came out and then the industry decided that it was the model by which every other MMO to be developed had to follow, so no real effort in the corporate MMO industry has been put towards a next gen sandbox. There's one being developed by an independent group whose kickstarter campaign was successful and it is in development now. Embers of Caerus. Another one, Arch Age... But they are several years away, so we must endure themepark MMOs for a while yet.
Even SOE is returning to it's roots now with TOR losing all those subs, that quickly. Read somewhere where Smedley took EQnext back to the drawing board (due to existing development being nothing more than a next gen WoW clone), scraqed existing development, and promised the "largest sandbox ever created" when it does come out. So the AAA studios are starting to get that they have to be different than WoW now, or people will just go back to WoW. No new-launch MMO can compete with WoW and it's 8 years of post launch content/additions/systems and even Jackalope (head developer at Cryptic) said after STO that people will not give years anylonger for a newly launched themepark MMO to catch up to the competition. That, I would imagine is due to the competition and the newly launched are priced at the exact same amount. Easy economics, when you get more for the same money, the consumer gravitates to more.
I'm actualy looking forward to the shift in the MMO industry away from WoW style copy themparks. Hopefully, we'll get some more creativity again. And creativity and quality will be rewarded by subscriptions which was Bliz's original gameplan in the 1st place.
TESO could very well fit that bill. Skyrim includes enough sandbox via housing, exploration, crafting, stat increases to everything, limitless toon building, and immersion to be that "next gen" themepark/sandbox mix that I would hope would take care of everyone's wants and wishes. The only concern I have, is that Zmax is starting to limit some of that for developmental time restraints. (such as no housing in at launch) My wife picked up Skyrim just after I did and she has already stated that without housing, she doubts she'll play TESO until it's got it. Some in my old SWG guild (that are now playing Skyrim and getting the social aspects from my vent server while ev1 plays a single player game) have said the same.