Jeez, you really love this question Brainglutton - I think it is at least the third time you’ve posed it. Not criticizing, mind you. It deserves its own thread if it interests you this much :).
But sadly my very nature leads me to respond to it again in essentially the same way, just as yours compels you to keep asking it. We’re all slaves to our impulses ;).
Pretty close to nil.
WAG obviously, but pretty low. Maybe. Kurdistan might prove an interesting temptation/exception.
As to why:
Lurs, Mazandarani, Gilaki, Bakhtiyari - From a nationalistic POV about as distinct from Persians as the Provencals are from the French. Luri/Laki and Bakhtiyari are both pretty close to Farsi ( though the mutual intelligibility is apparently limited ), Mazandarani and Gilaki a bit less so, but all of these populations are functionally bilingual. None of them are particularly restive that I’ve heard, other than perhaps the normal mild resentment at cultural domination from the center. Heck the Pahlavi Shahs originated in Mazandaran.
Azeri, Turkmen, Qashqai - The co-dominant Turkish minority. Essentially the same folks with marginally different dialects at best, in different regions and in the case of the Qashqai a somewhat different cultural milieu ( the Qashqai, to some extent like the Bakhtiyari, is a young cultural grouping, not so much an ethnic one - a nomadic tribal confederacy that formed in the 18th century ). All with significant investment in Iran as a state, many of them bilingual. The old ruling dynasties of Persia were Turkic and descendants of the old Qajar house ( whose tribe was deliberately divided among both the “Azeri” in the west and the “Turkmen” in the east ) and their relatives proliferated and formed a good chunk of the Iranian upper-class even under the Persian Pahlavis. Azeris hold high positions, still, in the government.
Granted there has been some regional restiveness revolving around issues of Persian chauvinism. There was also some related tension between the dueling Grand Ayatollahs of Khomeini and Shariatmadari ( an Azeri ), who did not get along theologically. But they’re dead now. Overall my impression is that accomodationists are still far more significant than secessionists.
Baluchis - Not strong enough to go it alone in Iran and U.S. ally Pakistan would foam at the mouth at any such suggestion.
Arabs - Oddly enough the rise of an Shi’a Arab theocracy in southern Iraq might strengthen secessionists in Iran. There has been some limited signs of growing restiveness ( or at least more active PR - sometimes it is hard to tell the difference at such a distance ), again probably mostly a reaction to Persian chauvinism. However they were notoriously unresponsive to SH’s attempt to rally them under the banner of pan-Arabism back in the Gulf War, so one wonders how widespread any resentment might actually be towards their co-religionists and countrymen.
Beyond that apparently the ethnic populations are heavily intercalated in Khuzestan, so teasing that apart would doubtless be rather messy.
Kurds - They most historically restive population, but considerably more marginal than in Iraq or Turkey. Very unlikely they could pull off any sort of secession on their own. The U.S. might be tempted to merge it with Iraqi Kurdistan ( assuming it would and could successfully invade Iran and bring about such a drastic partition - something that at the moment at least I rather doubt ), but I dunno if they’d actually go through with it.