Re: Trek XI's implications for future Trek novels (major movie spoiler
The long-range transporter thing could have been 'acquired' from the Dominion - or at least worked out independently once the Federation had documented that the Dominion had shown it could be done (by a power that aren't so far advanced compared to the UFP that it would take as long a time to catch up as it would to, say, the Iconians).
We saw an interstellar subspace transporter used by DaiMon Bok in "Bloodlines" on TNG. We know the technology exists in the early 2370s; it's just not commonly used because it's dangerous and extremely power-intensive. Which isn't inconsistent with its use in the movie, given the extreme urgency of the situation (although the power demands are hard to reconcile with beaming from a shuttlecraft).
The version used by the Dominion gives no indication that it's dangerous - but then, I suppose the Vorta and Founders would hardly want to reveal any such flaw should it exist in their version of the technology.
And that would still leave the difference that having the custom-made systems that the Dominion would have in place to make such technology operable and making do with jury-rigging a more primitive Federation model would make...
I suppose that's conceivable, but it seems unlikely to me. After all, if there were Vulcans scattered on multiple worlds, they can't all have had the same culture and the same values. They wouldn't have all made the same decision at the same time. As a student of history, I find the idea of a diaspora reversing itself to be highly unlikely. Even if the population of offworld Vulcans diminished in the 100 years between ENT and this, I doubt it would've diminished to 10,000 or less.
To me, it's simply Occam's Razor. The simplest solution is that Spock was upset about losing his planet and his mother and made an exaggerated remark about the condition of his species.
Well, I could think of two things:
*It's not guaranteed that even the pre-Federation Vulcans had an overly large series of offworld colonies to begin with.
They may have had just enough to run whatever military outposts or listening stations they deemed necessary, as well as had the odd P'Jem (legitimate or otherwise) to provide cover - but unless they were willing to sink enough manpower, fleet assets and logistical assets into defending them, I'm not sure how many major colonies the Vulcans would have wanted to establish.
They wouldn't be in the business if setting up private colonies the way humans do - and how many worlds can they afford to build up into major colonies while ensuring their security from Andorian or Klingon occupation?
Plus, while there may have been a somewhat notable community on Earth, that may not be overstated - and they seemed to make more of a deal of living in their compound, rather than mix with the locals - and is still probably more than would have chosen to live on Andoria or Tellar Prime or Denobula Triaxa, since none of those worlds serve as the seat of the UFP institutions.
*Even if there were a larger diaspora in the Federation, there's no guarantee that Vulcan society would consider them to be their own.
Take Japan, for example. There are millions of
nikkei (Japanese-descent people living outside of the archipelago) worldwide, and have been for over a century - but culturally, they are not quite considered the same way that, say, someone from Ireland or the UK might consider Irish- and British-descent peoples in places like Australia and the United States.
Indeed, since Japan does not permit dual citizenship, those expats are that bit more separated legally than, say, I as an Irish citizen living in Canada would be from my home island.
(Within Japan itself, there are often-hidden issues concerning non-
wajin people living there, be they Ainu, Ryukyuan,
zainichi Korean or Chinese, Buraku or others - and those who have mixed ancestry don't always get a better deal than a certain fictional half-Vulcan got on the world he grew up on.)
If Japan was wiped off the face of the Earth tomorrow, there would be the wider
nikkei community, yes - but the back of the 'home' culture(s) involved would likely be broken, and would be as hard to restore as 'New Vulcan' will likely be.