How could that happen though? The main quest is stopping Alduin from eating the world. How many alternate endings could there really be? I can't even think of one way to do that, let alone multiple ones. I think if they did come up with more than one, it would cheapen the feat of stopping him if it could have been done in so many different ways.
This was my thought. The main quest seems pretty much "Win or Die". Yeah, there can probably be different outcomes to some of the other plotlines, but they're not the main quest. :shrug:
(what I'm trying to say, I think..... without a big wrap-up "ending slideshow" like the Fallout games, there's no real need to tie all the sidequests into the main one. Heck, without the game having an "end", you may finish the MQ before the major sidequests. So, unless it's Morrowind-like, in that you need to gain the support of certain factions to beat the Big Bad - in which case, it's all just more main quest, not sidequests - I can't see them being strongly connected.)