Honestly, while i was reading this book i had one thought coming to mind time and again - what was even the point of turning the Wall off?
It mentions Stone saying something along the lines "We have to act now, if we wait more everything will be lost". I don't believe Stone cared enough about FedSuns to rush to their rescue or that he was afraid of Republic enemies uniting any time soon - that was definitely not the case.
Supposedly Republic had a large enough military force to do whatever it was they planned to, but what have they actually achieved? Lost time and resources on Remnants (which was ultimately useless since the entirety of the Remnant forces was wiped out anyway, not even halting the Clans), unsuccessfully campaigned against Wolves, Capellans and Combine.
The book does not really mention any RAF victories, only their attempts to contain the attackers - something they wouldn't have to do with the walls still being in place. Across Dark Age books it is mentioned several times that republic intelligence was able to go beyond the wall, so they had at least some estimation of the forces of at least Falcons and Wolves who they knew would jump on them immediately.
Even if we assume Stone forged a deal with some Clan prior to the whole Wall going down thing (who would be interested in a deal afterwards with a clear way to Terra?), what was he to gain from that? Why not invite that Clan into the Prefecture X to work on a joint plan to un-****** the Republic? My only guess would be he knew that someone was watching the Republic, waiting for the Wall to go down, and he placed his bet on that someone to arrive sooner.
It clearly is not any of the Clans heavily mentioned in this book - none of them is interested in a deal with the Republic. Wolves and Falcons can just take it, despite all Alaric's caution his Clan is strong enough to do it. Foxes won't have any profit. Bears are much more concerned with their internal affairs, judging by the fact they did not act to reclaim lost worlds when the population was found to be treated fairly. That leaves the Clans not mentioned - Ravens and an assortment of half-killed or far away entities. The Ravens have the fleets, but would they want to lose a sizeable chunk of that on what basically is a coin toss?
That leaves us with two options - Wolves find a way in and the next book ends the hostilities around Terra in a single chapter - trial of combat against Stone, Alaric takes the planet, it is universally considered to be a bad move and we have another 10 years of combat; or some out-of-nowhere faction finally arrives and something completely unpredictable happens.