i wouldn't mind an elder scrolls RTS. i dunno about a diablo clone, they're rarely handled well.
TES only has "hack-n-slash traits" because it's never had a good combat system. they really need to work on that.
An RTS for Elderscrolls would be pretty cool. Each race with different buildings...Imperial forts, half timber houses, camp tents, Dunmer strongholds, Mushroom towers, ald-skar or w/e, Argonian Hist...different units like Telvanni mages, Bosmer scouts, Ashlander skirmishers, Imperial legionnares. The gameplay would be different enough to warrant a separate style of game.
But yea...third person hack and slash, with mobs of enemies? No. Dungeon crawling, fast paced twitch combat? Sure. A narrative story line isn't so important as simply a narrative world, like Morrowind was, with conflicting politics, racism, economics (fights over mining rights and smugglers of all types) I feel like that (aside from the perspective) is what makes a hack and slash different, and inferior to Elderscrolls.