I think this question really hinges on too many variables that we don't know enough about.
Which is good for allowing for broader speculation...
For example, what did the Dominion "surrender" mean. Was it a promise to end hostilities and stay in their own quadrant? Was it more?
...Was it less? We hear it stated that the hostilities end there. We don't hear it stated that the Dominion would withdraw from anywhere, not from Alpha, not from Cardassia.
Even if the Dominion's surrender wasn't absolute, we still captured ships and learned from their technologies. Do any of those technologies have implications for ship design?
In a diverse galaxy, probably less than we might expect. The Dominion surprised Starfleet with exotic guns that penetrated shields for a while. Supposedly, any future opponent might do likewise, with both Starfleet and the Dominion equally surprised.
Then again, the Dominion still exists. Equipping to stand in readiness to stop it again, perhaps seven decades from now if the wormhole remains shut for invasion fleets but the galaxy remains open, would seem prudent. And the Feds may well believe that equipping to face the Dominion as it stands in the 2370s will be enough to stop the Dominion as its fleets stand in the 2440s. After all, not only is the Dominion a conservative force, unaccustomed to rat races and evolution - the ships launched across open space to fight the Federation would represent the 2370s standard of their launching day, not the potentially higher standard of their arrival date.
It has been suggested that several times over the course of history Starfleet has learned more about how a ship's shape affects its warp field allowing them to build faster, more efficient ships by reshaping the hull (similar to how we learned more about drag for naval vessels during the last century, changing the design of ships' hulls). So did Starfleet learn something that makes existing designs obsolete?
Probably not speedwise, as the Dominion wasn't credited with faster ships. And overall we learned little that would make Dominion ships better; the differences our heroes commented on where on user interfaces and their inconvenient design philosophy.
Even if the Dominion didn't turn over all of their tech, does Starfleet have permission to explore the Gamma Quadrant? Are the Federation/Klingons/Romulans expected to start patrolling Dominion space in the GQ? Because that is going to take a lot of ships.
Sounds dubious. A stranded beachhead force of the Dominion nearly outproduced all of the Axis of Alpha put together; the main Dominion industries back home would be capable of pumping out even more, making any show of force or associated demand by Alpha utterly futile.
On the other hand, other technologies are going to have a profound impact on travel. As I noted elsewhere, Voyager gathered a lot of data on a device called a subspace catapult that its designer described as "able to hurl a ship across thousands of lightyears in the time it takes to say 'hurl a ship across thousands of lightyears'." And that's a game changer. Any ship in the Federation can get to any point in the Federation in the time it takes to get to the nearest catapult.
Might be this replaces soliton wave research. But other superdrives encountered by Janeway's team would offer more in the field of conventional "free" navigation, with greater potential for combat and exploration applications.
Plus, .... I actually haven't seen Nemisis yet. But clearly it sets up the Romulans for some pretty big changes.
Nemesis probably didn't change anything. There was a coup involving the assassination of the entire Senate. But that may happen on Romulus every second Tuesday except when it rains. The movie itself contains a sly reference to the regime of Romulus changing often, and always implementing minor policy changes that make short work of longterm plans. That's just the reality the Romulans have lived with for ages.
Is losing their home planet a minor setback for an empire that was largely decentralized and maintained a token population there while their most populous worlds were elsewhere? Or was it a crippling blow that wiped out much of their population and most of their government?
Ah, this happens in the nameless 2009 movie. And we can't readily tell. Losing the government may be trivial, as it already happened in ST:NEM and merely marked a palace coup at best. But a paranoid Empire might take care never to decentralize, and never to allow colony worlds to become truly self-sufficient. The Romulans might well be quite badly off in the aftermath of the supernova that cost them their homeworld.
And what (besides the Borg) was on the other side of the Romulans? What threats or opportunities were the Romulans keeping the Federation isolated from, intentionally or otherwise?
It seemed Romulans were operating outside the RNZ often enough in TNG, with little comment. Does this mean there's a legitimate back door there, perhaps? Is this what allowed them to do the Tin Man hunt, which then might be on the backside of the RSE?
Things were poised to change significantly immediately after the Dominion War, and we don't really know enough about what happened to know what that means.
Section 31 seemed to think the Romulans would fare well while Klingons and Feds would be weakened. With the Romulans now hurt, all bets would seem to be off even in that regard.
Writers of late 24th century events are quite free to do whatever they please, I guess. Even including restoring planet Romulus somehow. Sure, she was lost, but in a time travel incident - perhaps the loss was inherently reversible? Nero for his part claims he "prevented genocide" by his actions in the other timeline; perhaps he preempted the destruction somehow.
Timo Saloniemi