I don't think Burton watched any behind the scenes footage or any Interview of JJ ABRAMS speaking about the 09 film or even watched the film with JJ's commentary.
Well, that's just non canon meta-information nobody really cares for and that has just been said to make hardcore fans less butthurt. The old timeline is gone, doesn't matter what someone says off screen. If they wanted to make it clear to everyone, they could have said it within the film itself.
How could it be gone?
If someone decided they wanted to make a TNG film continuing on with the TNG story where it last left off, they could do so and nobody would say:
"Hey!! That timeline doesn't exist!!!"
Instead they will just say: "Hey! Another TNG story!"
As I said before in another post, someone could certainly continue the TNG story if they wanted. There is nothing "artistically speaking" that is stopping them. Whether or not it would be commercially viable is another story, but Abrams' films don't adversely affect that commercial viability, either.
What it comes down to is this: Do you actually believe that it is no longer possible to make another TNG story based in the old TNG universe? And if you do, are you saying it can't be done solely because of the story that unfolded in ST2009?