I can't say for certain what the controls were like for Battlespire, but I assume since it started life as a Daggerfall expansion pack, it at least shared similar controls. And Morrowind and Redguard's art styles are fairly similar, although of course Redguard is a few years older. They also all share a development team, at least in part.
The books don't count. They're not games. You might as well say that the Alduin statue that came with the Skyrim collector's edition isn't Elder Scrolls because it's a toy.
TES Online's art style doesn't resmble an Elder Scrolls game. The gameplay doesn't resemble an Elder Scrolls game. There's less player freedom than you'd find in an Elder Scrolls game.
I'm not necessarily saying it'll be a bad game, as I obviously haven't played it yet. What I am saying, is that from the information we have so far, there's nothing outside of the setting that resembles any other game in the series, except maybe Arena. And Arena was pretty damn generic.
KOTOR and Battlefront are both Star Wars games. Completely different gameplay and mechanics, but all set in the rich Star Wars universe.