I wouldn't be surprised if Bethesda hires Jeremy Soule for the Elder Scrolls V again. While they may not have used his work for Fallout 3, this might be because the styles he has most experience in wouldn't really fit the Fallout setting very well. After all, most games with Soule's music that I've played are fantasy games, and music that works for a world of Medieval knights and elves and goblins simply isn't going to fit in a post apocalyptic wasteland. I doubt it means Bethedda doesn't want to use him anymore, they just got someone they probably felt would be more suited for the job.
But in any case, I'd say Jeremy Soule's work on both Morrowind and Oblivion was as a whole okay, I really liked the main theme of Morrowind, most of the other music I felt varied between good but not exceptional and okay. Although I didn't like Oblivion's theme quite as much, I still enjoy it, and whenever I get back into either Morrowind or Oblivion, hearing the theme song is a good way to get me into the mood for the game, the rest of the music in Oblivion I actually liked somewhat better than for Morrowind, but this could just be because towns and dungeons have separate music from wilderness music. All in all, though, I could accept them using Jeremy Soule, but if they decided to go with someone else... it would depend on the results. I have an idea of what I can expect from Soule, but if they hired someone else, it would give them a chance to potentially provide something better, the results, however, could also be a step backwards, whoever they go with, as long as the composer can provide a soundtrack that's both good and fits the game, I'm fine with it.
Really, though, the biggest change I want in music is more music changes depending on location and what's going on at the time. As in, different types of location should get different sorts of music, and I'd also say important events deserve their own music. While having town and dungeon music as well as exploration and combat music was an improvement over just the latter two, it still could be done better. Taverns for example should feel distinct from city streets or houses, so they should also get different music from these places, and the music in a lush forest shouldn't sound the same as a barren wasteland. I'd also say that battles against boss type enemies should have different music from generic fights, and fights against really weak enemies like rats and mud crabs, I'd say, should perhaps not change the music at all, for one thing, dramatic combat music seems inappropriate for such an easy fight. For another, it's kind of annoying when the game switches to combat music suddenly when a rat starts charging at you, than with one hit, you kill the rat, and immediately it goes back to adventure music. This tends to break the flow of the soundtrack, and just makes me wish those rats would leave me alone more than I already do.
I don't understand why people hate his battle music. I agree he is better with exploration and city music, but I think his battle music is pretty good.
I wouldn't say I hate it, I'd just say that most of the battle tracks he has composed are kind of boring, which I guess is fine when you're just fighting rats, but when I'm fighting against the final boss, I generally like something a little more dramatic. Yet if I add more epic custom music, than I end up hearing dramatic fight themes play while a mudcrab attacks me.