It's also probably inevitable. The Romulans spend most of the TNG era teetering on the edge of opening up and rejoining with the Romulans, and with the Klingons so weakened by the Dominion War the collapse of their empire is probably likely. The Cardassians are gonna need help rebuilding, which the Federation will be the first to offer, Bajor is already basically a member state. The Ferengi Alliance under Rom is going to be much more open and close with the Federation, especially with the Nagus' son being a Starfleet war hero.
The Breen will be happy to join once Starfleet finally denounces the war criminal Flox and pay reparations for their role in past atrocities.