This was definitely one of Sulla’s great strategic masterpieces, if you ask me... even if the figures on casualties are wildly underestimated on the Roman side. We can be sure that Sulla’s army was drastically outnumbered, and in the middle of the whole affair a bunch of refugees from Rome showed up, including his family, bringing the news that Rome had been taken by Marius and that he had been declared an enemy of the state.
So, let’s say he loses... completely. His army is annihilated, and he himself suffers some grizzly fate at the hands of Archelaus or perhaps he is shipped over to Asia for Mithradates to decide how he goes. What happens to the refugees? Does Mithradates attempt to cooperate with the new regime and hand them over as a gesture of good faith? Will Rome even take a gesture of “good faith” from him?
From what I can tell, despite the death of Gaius Marius, the only people left to challenge Cinna would be Quintus Caecilius Metellus Pius/Marcus Licinius Crassus in Africa, who, without Sulla, probably don’t stand much a chance in Italy, with Cinna’s regime being backed by many within Rome and the Italians.
At this point in time, the economy of Italy has been gutted by the Social War and the Marian Civil War. The east would seem to be gone, and Mithradates would likely be able to consolidate his holdings there by ordering further murders of Romans and Italians there. I imagine that Crassus and Pius are going to try and make a go for Rome... or for Greece/Asia and THEN Rome (using the funds of the former to fund the latter). But, it would seem to me that any attempt to take Rome/Italy by way of reconsidering might a) be really stupid and b) mean that they will be raising armies of foreign (Greek/Illyrian/Numidian) auxiliaries to do so. If they can manage a victory in Asia and Greece, which I think is extremely doubtful, how will the people perceive them upon entering Italy with such an army? Or... would they even attempt this? Would they be more likely to stay behind in Africa and hold out there the way Sertorius did IOTL in Spain? Or would they make for Italy before the east and try their hand at yet another march on Rome?
Personally, I don’t think they can take it. And if they can’t take it, what happens to the east? Cinna and his regime likely will not let that whole debacle go quietly, but... if Mithradates can consolidate Greece with Sulla dead, I don’t see the Romans being able to take it back. And if they do, I think that the issue of reclaiming it could become so contentious among the political parties that it could collapse the Republic.