The Klingons would be with the Federation, but the Romulans aren't a given. But even if they are... I don't see it making much of a difference. The three of them nearly lost to the Dominion with just the resources of Cardassia and later the Breen at their disposal as an industrial base to build their fleets and breed Jem'Hadar.
So after their humiliating defeat, I don't see them, even with Odo among them, giving in to an era of good feelings towards the solids. Heck, even Odo was blatantly resentful towards the morphogenic virus. Now factor in that they're holding the Female Founder hostage indefinitely for her "crimes" and by her own admission one changeling is more important than the whole Alpha Quadrant and I think you have them immediately gearing up for the next fight revanchist style.