I honestly didn't feel pressured to do Oblivion's main quest. In fact I still haven't finished it (I will eventually). I did dozens and dozens of other quests and finished the Fighters/Thieves/Mages guilds all before touching Kvatch.
I often do that too, however, from a role-playing standpoint, it can be hard to justify going off to do whatever I want while everyone is telling me that I need to hurry before its too late, in Oblivion, before you even leave the sewers, you're told to "waste no time" and to take the Amulet of Kings to Jauffre "immediately", and upon reaching him, he tells you to go to Kvatch immediately, implying that if you don't get there quickly, it may be too late, and it seems like there's not one moment where the game isn't trying to urge you on, the only time the pacing seems to really slow down somewhat is when you're told to find a Daedric artifact, and that's only because for that quest, you need a little more time to find an appropriate artifact. I still try to approach the main quest at my own pace, though, in part because, from a role-playing standpoint, it's also hard to justify a level 2 character stopping a Daedric invasion and being named Champion of Cyrodiil.
In this respect, I'd say that I prefer Morrowind's approach, because it wasn't constantly trying to rush you. The story seemed to be written with the idea that players would want to take their time in mind, and not only did the story not contradict the fact that you can take as long as you want to do the main quest, it actually actively encouraged you to take your time, go out and practice your skills, do side quests, or get better equipment. And it was good advice, since Morrowind was a game where you could very well find yourself facing overwhelming odds if you didn't gain enough levels. In Oblivion, on the other hand, it seems like someone neglected to tell the writers that the game is supposed to allow you to take your time, thus, we get the game always urging you to go to your next objective as quickly as possible. Which not only doesn't make much sense from a role-playing standpoint, but also serves to kill much of the drama the sense of urgency might have created because you know that despite what people tell you, the world isn't going to get any more screwed than it already is if you ignore the main quest.
Now, I can understand wanting to have a sense of urgency, from a narrative standpoint, it's a common tactic to increase drama in other mediums, like movies, books, and television. However, what we need to remember here is that games are not movies, nor are they television, and they're certainly not books. One key difference between games and these other mediums is that games are interactive. In a novel or movie, you won't see the protagonist running off to go pick flowers when there's some urgent business he knows he should attend to, usually, if you do, then you'll probably expect this move to have concequences later on, but in any case, it would only happen because the writer wrote the story that way. In non-interactive mediums, writers can dictate the actions of the characters, and characters can approach the situation at whatever pace the plot requires, of course, due to the rules of dramatic convenience, if there is some sort of explicit time limit the characters will always make it at the last minute, you never seem to see heroes disarming the bomb when there's still thirty seconds on the timer, or stopping the evil cult when there's still a week before the stars are in the right alignment in the sky to revive their ancient god, it's always at the point when just a second longer, it would be too late, but we're not here to discuss that, so back in tropic. In games, you have to account for the fact that players might not be doing what the story assumes they should be. In more linear games, this isn't too much of a problem as there's only so much you can do other than progress in the main story. Some players might overcome obstacles more quickly than others, or some might stop to admire the scenery while others would just rush on to the next objective, but there's still generally no way for them to stray from the linear path. And its easy to write the story in a way that implies urgency, but doesn't contradict the gameplay because it doesn't explicitly tell you HOW urgent it is, unless there's an actual time limit, at which point, you really have to hurry. The main problem comes in when you give the player freedom to ignore the main story at any time, like in the Elder Scrolls, at which point, the best approach is to create a story that supports this, I think, otherwise, you get a case of http://tvtropes.org/pmwiki/pmwiki.php/Main/GameplayAndStorySegregation. To some degree, it's hard to stop this from ocurring, of course, but it's something that should be avoided when possible. I'm of the belief that the story of a game should serve to complement its gameplay and explain why things are the way they are, rather than contradict it and make it seem like the gameplay and story are taking place in entirely different worlds.
At the same time, though, with dragons flying around Skyrim attacking cities, I can't imagining the game not to try to pressure you at all, so I'll hope for something in between. Nameplay, the game should start off without a strong sense of urgency, kind of like how Morrowind's main quest played out, giving you a sense of where to go, but not making you feel like you need to go there as quickly as possible. Then there could be some buildup as the story advances. Once you start doing the early quests, the story might still not give you a strong sense of urgency, but could start to hint at the gravity of the situation, most importantly, though, at this point, the story needs to make you WANT to find out more, as you get further, it could start to give you a more concrete idea of whats at stake, and that if left unatended, the problem will only get worse, then later on in the story, towards the climix, THEN they can start doing the whole "The world could end if you delay!" thing. This way, players won't feel like they're being forced into the main quest from the start, and it still feels natural if you choose to ignore the main quest, but once you get more involved with the main quest, you still get the same false sense of urgency later on.
Although in the end, as long as they don't completely ruin the open world exploration by having an actual time limit on the main quest, I can live with whatever Bethesda does.