It would depend on when the timeline diverged. But speculating...
If Dulinor never went to Omicron and let Virus loose, he probably would have taken the throne with the Coronation fleet. Though considering the state of the Imperium at that point, he would have added a new meaning to 'Phyrric Victory'. My name is Ozymandius indeed....
'Real Strephon' would be long gone. The only reason he lasted as long as he did is because Dulinor and Lucan had better things to do.
Brzk wasn't doing too badly. Playing nice with the Julians meant he would have a trading partner, a Vargr shield and defences. His problems would mainly be internal racial ones (Humans vs Vargr).
Margaret would be treading closely to following in the footsteps of Marie Antoinette. Happily oblivious to problems as long as the trains run on time and rather blase about slavery if her friends and business associates are the ones doing it. The only reason she was even a contender is because of the magical cadre of psionic ninjas called IRIS (who had the capacity to pull entire fleets out of their posteriors if needed).
The Solies appeared to be as incompetent as ever and went nowhere. Even with 5 sectors of 'Safe' they managed to get continiously spanked by a few worlds in the Vegan district and the Daibei subsector. I they can't even manage that, then forget their delusions of Empire of Man mk2.
The K'Kree tried a bit of gunship diplomacy during the rebellion (in Survival Margin TAS news IIRC) and got spanked. If even a crippled Imperium can give them a hiding they wouldn't be much problem.
The Aslan could be interesting, especially if Craig is paying the Ihatei as mercs. What will Craig do when the bill comes due once the fighting stops. They probably wont poke the Sollis as that would cause the Solis to band together.
Norris would be in a bind. Without them being the 'sole survivors' things would get messy - he could be found out being a fake and blackmailed. A good chunk of the nobles would support the new emperor so his reforms would never happen. Vargr and Aslan would say 'Hmmm, nice land/loot you have there'. And then when a crapload of Zhodani start swarming in...
The Hivers would all be claiming that it ws their manipulaton when brought down the Imperium, while the Sword Worlds would stomp Darrians into mush (GM fiat - because I dont like them :devil
when the star trigger is found to be a load of crap (again).
And then you have the autonomous districts/pocket empires popping up everywhere in the outlands/wilds who probably wont be to pleased to become part of a broken Imperium who abandoned them.