A peace deal or at least an armistice is necessary to set the ground rules going forward. If utterly defeated, the IRGC leaders will still want assurances that they will not be hunted down and killed.
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Their own people will kill them. Their best move is to make a bee line to Russia or France.
Russia is plausible, but Russians charge dearly for a safe exile. China might accommodate them, but also for a price. The usual practice is to squeeze exiles dry and then tell them they are on their own. Most Iranian regime exiles would prefer to cut a deal with the US, get new identities, keep some cash and settle in a secure place.