I actually disagree with you on Oblivion. The problem with creating a game for the next generation is that you don't entirely know what it's going to be capable of. You end up going big and scaling back which is exactly what happened with Oblivion.
The fact that both Oblivion, Fallout and Skyrim were released for the Xbox 360 speaks wonders for how much they've accomplished from a technical standpoint. PC gamers continue to push Skyrim's visual limits so long as you have the hardware to back it up.
With Bethesda staying fairly quiet about what they're currently doing, and with "next gen" consoles being out for some time now, they're probably going to accomplish a lot from a technical standpoint with their next title.