oblivion has drugs in it.
oh and religious cults
So did Morrowind, and can you guess what it's rated? T, that's what.
And yes, as has been said, Oblivion was rated T as well upon release, than ESRB changed this rating, there seems to be some debate as to the reasons of this and I have no wish to participate in it, but it DOES show us that when ESRB first examined the game,
In any case, Bethesda is not aiming for a specific rating, if what we're told by them is true. They make the game they want, and let it get the rating ESRB sees fit, and that's what I'd want them to do. Because whether you want a T rating or M rating, going out of your way to get a specific rating may lead to developers making choices that could be harmful to the game for the sake of the rating. If you aim for a T or lower rating, then you may have to cut out some things so that it doesn't get anything higher, but if you decide to get an M rating from the start, you may need to add in unneeded swearing or a shot of a briast that serves absolutely no purpose just so it can get an M rating, and is that really better? As a player, the main advantage of M rated games to me is that there are fewer limitations as to what the game can have in it that way, but that's only an effective selling point if the game actually benefits from its "mature content". If the developers just tack on some pointless swearing purely for the sake of an M rating, though, not only might it not benefit the game, it could even become distracting as it does not fit with the feel of an otherwise tame game.
Still, Oblivion did seem a little too tame for an M rating, I agree, it basically felt like it only barely warranted its M rating, in fact, it felt more like a T rated game with a few more severed heads thrown in. So for Skyrim, I'd say bring on the blood and gore, I wouldn't even mind nudity if it isn't used too gratuitously, though I'm sure that won't happen. So long as everything is done in a way that's appropriate rather than being handled in a "Here's some blood and gore for you to gawk at." sort of way, I do believe Skyrim can benefit from being less conservative in the mature content department than the two most recent Elder Scrolls game.