Hopefully, a Trek universe forever changed. Stories about surviving Romulans who actually face a struggle, instead of just catching a shuttle to Romii, replicating all their old stuff and living happily ever after with 20 billion other bowlcuts.
I still don't understand how, in order to be affecting, the destruction of the planet Romulus can't leave very substantial numbers of Romulans alive on worlds other than their homeworld. Non-plausibility of Romulan conquest not being accompanied by Romulan settlement--
as explicitly described in the novelverse--aside, the destruction of he heartland of any major power on 21st century Earth that left newer acquisitions untouched would still have huge effects. Yes, there'd be plenty of United States left if the Eastern Seaboard was
razed by the defense platforms, but the remaining Americans would be left reeling (as would the rest of the world).
There's still plenty of space for struggle in that environment; more space, I'd say, since there's still a point to it all from the Romulan perspective. "If nothing's left, what's the point? May as well reunify with the Vulcans."
Anyhow. Let's work from the assumption that there are very large but astrographically and culturally separated Romulan populations off of Romulus, alongside populations of various subject and allied species. (The Kevratans were conquered, the Elohsians of
The Romulan Stratagem joined.) What next?
How about that Klingon takeover from the alternate future of "All Good Things"? That would be amazing.
The destruction of Romulus might well create enough chaos for the Klingons to exploit, but for that to happen you'd also need the Typhon Pact to fall apart or not intervene in the conquest of its largest member-state.
Same thing for the post-STXI Vulcans. If there are billions more Vulcans out there, the end scene where the two Spocks meet and discuss the future is rendered moot. It cheapens the events of the movie.
You've made a convincing argument in favour of Vulcan culture being pretty concentrated on the Vulcan homeworld, but the argument can't be extended to the Romulans IMHO given the documented size of their empire in TV and the documented colonization of non-Romulan worlds by Romulans in the novelverse.
Otherwise you might as well write a post-Destiny novel where you explain that none of those worlds were really destroyed - the Borg just orbited them for awhile and Picard, caught up in the moment, assumed they all would be.
Of course they were destroyed since they were explicitly described as destroyed, and they were destroyed with exceptionally high death tolls, too: only a few ships escaped Barolia, Choudhury and Wolf thought of Ramatis III as a tomb for a civilization of almost a billion people, Picard was impressed with the efficiency of a program that evacuated more than a million people from a Deneva that was home to a couple of billions, and so on.
In the case of Vulcan, you've made fairly convincing arguments that Vulcan civilization wasn't very expansionistic and that there weren't many Vulcan colonies of settlement. I'm inclined to agree with Christopher that the figure of ten thousand refers to evacuees from Vulcan as opposed to the total number of survivor, but a Vulcan survivor population totalling in the low millions is plausible to me.
Maybe
Sigma Draconis V, mentioned in
Cast No Shadows among other places as a new Vulcan colony, was the one selected? Sigma Draconis and 40 Eridani are in the same neighbourhood, and are even broadly similar from the perspective of stellar class and age and whatnot.
Those argument don't hold for the Romulans. Let's exclude the novelverse documentation of multiple populous colonies for a moment. For centuries the Romulans have been aggressively expanding across the galaxy, as they believe it their inherent rght. Why, if their territory extends dozens of light years from their homeworld and presumably includes many environments that are attractive destinations for settlement (environmentally, economically, et cetera), would there not be substantial numbers of Romulans living permanently off their homeworld?
Romulan civilization--starfaring, expansionistic--has made the Romulans as relatively immune to local catastrophes. Humans enjoy the same luxury, too. In an exchange in
Before Dishonor between Leybenzon and Kadohata, the Cestus III-born Kadohata points out to Leybenzon that even a Borg supercube destruction of Earth wouldn't doom the human race since there were far too many humans living offworld for the species to be done in by that. (She shouldn't have had to make that point to Leybenzon, he Worf's fellow native of Galt, but that need was one of Leybenzon's many flaws.) The Romulans are in a similar position; if they didn't, you'd need a pretty compelling explanation as to why not.
