For all we know, the peace treaty ceded Cardassia to the Dominion...
Basically, I'd assume that the Klingons would want a piece of that planet, after having gone to all the trouble with conquering Cardassian wars in the past conflicts. Never mind how poor in resources or full of potential insurgents, the world/system would be a prize of prestige for them. Romulans might be less passionate about it, withdrawing to behind their Neutral Zone once again and waiting for Nemesis to happen. Unless they wanted a base close to the wormhole, that is. But perhaps the wormhole no longer is open for traffic, as part of the peace stipulations?
The Federation would have every incentive to try and help the natives, and to form an alliance or offer membership candidacy. That would probably continue even if Cardassia decided to again go for something else than a civilian government.