Hard to tell. Another Afghanistan (perpetually failed state) or the US/West/Israel (along with GCC aid) imposing a new regime on Iran that will not act in a hostile manner and a regime that we can all benefit from. That or the regime somehow surviving but getting more hardcore and more isolated, sanctioned etc.
However the regime is not very popular in Iran - I would guess that the majority of them want them gone - remember the regime just recently killed 3000-30.000 of its own people - gunned down like sheep - half it not more Iranians are not really religious and are living in poverty, isolation etc. They want a better life which I do not blame them.
So if you ask me it all depends on what will occur long-term. Obviously a failed state like Iran turning into Afghanistan next door is not ideal for the region - KSA/GCC included (even if we do not share a direct land border and will be impacted far less than say Turkiye or Pakistan) but I do not believe that the regional powers and West/Israel would allow it to occur.
On the other than the state could also disintegrate by itself. You have the Baloch who are a completely different entity on its own compared other say Tehran and the Kurds (active separatists for decades in those two regions), the Iranian Arabs and other minorities. Pan-Turkic sentiments among Azeris is not unheard of either. In reality many of the Iranian minorities feel disfranchised and feel alienated towards Tehran and the Mullah lot.
If they get this tinpot "king" on the throne again (Pahlavi dynasty - created in 1925 by the Brits - some officer turned Shah overnight) we will likely see another extreme - instead of Wilayat al-Faqih cult we will have deluded Persian nationalism and hardcore secularism etc. I would love to see the faces of the pro-Iran regime lot in the Muslim world, Pakistan included, once that happens and they will be told to their faces what the "new Iran" thinks about them, LOL.
That leads me to another crucial point - Iranian society is probably the most divided society in the region with delusions being sky-high among both parties (anti-regime and pro-regime lot).
But as I wrote all of this is their own undoing. They started it themselves back in 1979. From day 1 they were a constant destabilizer and opportunistic meddler. Therefore I have zero sympathy for them and I hope that MbS played them as Washington Post (anti-KSA post-Khashoggi) claims.
Not sure if accurate but hopefully so even though nothing in KSA has been hit so far. Which is also very telling for various of reasons.
Likely fake news as I wrote (Visegrad 24 is paid by the Abu Dhabi regime) because nothing in KSA has been hit by the Iranian regime and no attacks either. Zero visual evidence in a country of almost 40 million is also impossible when everyone in KSA has a smartphone with a camera and we have one of the fastest and most stable internet connections on the planet.
If you ask me this is Israel trying to get KSA actively involved in the war. At the same time Iran is so desperate that they believe that by targeting the smaller GCC states, the leadership there will try to pressure the US into stopping the war. Stupid modus operation (typical of the Mullah regime) that will likely only backfire.
That should not be accepted. Is there any religious minority anywhere in the world that has such divided loyalties and who are attacking/instigating trouble within their own lands? Not even the Jewish diaspora globally acts this way whenever Israel is attacked etc. You don't have any other Muslim sects rallying for any foreign Muslim leadership. At most we are mostly concerned with our Muslim holy sites.
I am shocked at how stupid and ignorant those lot are. Have they been brainwashed to such an degree that they do not understand/cannot see 47 years of Iranian regime propaganda for exactly what it is?
Also notice how pathetic their propganda has been/is. They are claiming that they are fighting for Palestine/Gaza while they did not lift a finger for Palestine and Palestinians since 1979 and never attacked Israel even 1 time - until Israel attacked them severely on numerous locations themselves. Them replying is now propagandized as a "defense" of Palestine.
The reality is that we have a lot of low IQ people among us.