Why ?
I'm sorry but personally i don't want to see old stories retold in the sequel.
We've seen V'Ger, we've seen Khan, we've seen the whale probe etc etc
Let's see some new adventures.
But then again I'm one that doesn't care much about canon in relation with the new movies so...
I agree that new adventures will be a good thing. But I'm also saying that events in the trek universe like Vger are as sure to happen as the sun going nova in our real universe. Vger is coming. Vger was always coming no matter what happens to the Federation and Earth in the new trekverse.
It is sloppy writing to erase Vger from existence because no events in the new continuity exist to get rid of Vger before it arrives at earth. If Vger is erased, it means that there is no consistency in the new trek at all. Which means Spock prime should never have been there to tie both continuities together. Which means Abrams & co would be SLOPPY WRITERS.
I agree that events such as Vger are already in motion and will probably happen.
However they can happen off screen.
As for Spock Prime being there to tie continuities... this is an alternate universe\timeline he has traveled to.
For him all the events we have seen in the tv shows and movies have happened already in the Prime Universe and his existence or not does not depend on them happening again in the new universe.