Still, he approved and participated in the writing of a script that included Leonard Nimoy and intentionally set up the new timeline as a continuation of what had come before.
But it's not a continuation of what came before, except from Spock's point of view. Temporally, it is a
replacement. That is the only reasonable interpretation, contextually speaking, based on how time travel is depicted to work, canonically, in Star Trek.
No.
TNG et al still happen.
Yes, they still
happened, but that timeline would be destroyed (cease) after 2387, based on how time travel works in Star Trek. And that is
a huge problem for the novels.
The previous timeline is always destroyed and inaccessible, and does not propagate any further from the point of departure of the incursion.
The same thing happened in
City on the Edge of Forever.
The same thing happened in
Yesteryear.
The same thing happened in
Yesterday's Enterprise.
The same thing happened in
Past Tense.
The same thing happened in
Star Trek: First Contact.
...Not to mention every single time characters expressed the concern that if something changes in the past, the future will be changed. If that's not true, then who gives a shit? Sisko doesn't reassure Bashir "It's okay, at least all of our friends are still fine in our original timeline." Instead he's worried he has inadvertently destroyed the Federation.
This "Alternate Universe" thing is nonsense: We learn several important things about alternate quantum realities from
Parallels.
1. They are detectable and can be measured and recorded for later comparison. That's how they are able to find the right ship and get Worf back. Even in the 22nd century, the Mirror Universe NX-01 has the ability to scientifically assess that matter came not only through time, but from another universe, in
In A Mirror, Darkly.
2. Signatures are unique to each reality, and they don't change over time.
These facts mean that the Prime timeline no longer exists
anywhere.
Abrams could have chosen to explain in the film that the ships from the future had a different quantum resonance signature, but he didn't. He just had "time travel, time travel, time travel" because it's more accessible to his audience.
And we're not working by Doctor Who rules here.