I think an alternate timeline is what we're dealing with. Based on spoilers, Nero travels back to kill Kirk before he was born by destroying the ship that Kirks parents are aboard (the U.S.S. Kelvin). He fails but Kirk's childhood is somewhat altered by the loss of his father. However, he does still inevitably joins Starfleet. Therefore, we have a second timeline that would deviate from what we know about the time immediately preceding TOS, mostly in regard to Kirk. However, in the long run, not much would change, especially in Nero's time (the late 24th century, presumably).
Therefore, Nero travels back again in an attempt to destroy Vulcan and more radically alter the timeline. This attack on Vulcan was never supposed to occur and brings the TOS crew together differently than in the original timeline. Now, Spock from Nero's timeframe travels back to prevent Nero from succeeding in destroying Vulcan (but presumably cannot prevent the earlier attack on the Kelvin). He'll be more or less attempting to perform damage control.

So I don't think the original timeline will be entirely restored but we'll get a new, fairly similar timeline that in the long run (i.e. by the 24th century) but the events surrounding the timeframe of TOS will be marginally different and give the writers of this movie and the possible sequels some leeway to tell new stories involving the TOS crew. Presuming of course there isn't some sort of predestination paradox in the works (I do highly doubt that possibility). The original timeline is also preserved in a sense because everything that happened before has to have happened if Nero wants to change it. It's very existence is his motivation for wanting to change it.

This isn't really my first choice either, but in the long run, I think its the best option. Star Trek needs to be re-launched with the characters that are strongest in the minds of the general public, the TOS crew, and the story needs to be accessible to someone who has never seen Star Trek before.
The fact of the matter is we need new Star Trek fans. The existing hardcore fans are now too small a market to be worth targeting (which is a big reason why Enterprise was cancelled, although not all Trek fans were watching Enterprise by the end). If this movie isn't a success, it's game over. Paramount is going to stop producing Star Trek movies or TV shows for the time being because it's not going to be financially viable. The best we'll be able to hope for is some direct-to-DVD movies and the novels. It could very well represent the end of the franchise and I think we can all agree that the message of Star Trek, a hopeful future for humanity, is too important to let die.

So while this may not be your first choice for a Star Trek movie you want to see, it may be your only choice if you ever want to see what you loved about Star Trek again (not to say this film won't have what you loved about Star Trek, it's kind of hard to know that without seeing it). I'm not saying that you absolutely have to see it, but there's a lot of time between now and May and it would be best to keep an open mind. Also, I'd just like to say that I'm not targeting VaBeachGuy specifically, even though I realize it may sound that way. I really mean this more as a commentary to the fandom in general.

I just really don't like the idea of messing with the time-line and not correcting it back to what is already set as "history". Unless they have a really good way of making it all work so that TOS's time-line is still intact.

We have to assume that a major thing in Kirk's life was the 2246 massacre on Tarsus IV where he lived with his parents. If his parents are killed before 2246 and we see an underage Kirk of about 12 on Earth in a corvette then it looks like he won't be living on Tarsus IV to witness the massacre. That alone will change Kirk's personality to some degree and if he never lived on Tarsus IV then the TOS episode "The Conscience of the King" can't happen... but it did happen.

I really don't like this storyline at this point. If they don't have a way of setting things right then I don't think Trekdom will accept it and I don't care how many non-Trek fans they attract, if Trek Nation doesn't accept it then it will fail. That's the part that I fear Abrams, as a non-Trek fan doesn't understand. I fear that he's looking at this as a "stand alone" movie that doesn't have to pay attention to a history and doesn't have to worry about pissing off 80 million+ inhabitants of Trek Nation, possibly a lot more. I'm not sure what the worldwide count is.