alt Hacker NewsRussia isn't moving for obvious reasons (I don't think IRGC planners even expected them to move, Putin has made it clear a 100 times he is out of anything involving Israel). But that said Putin arguably did his job already by destroying Patriot stocks and thus putting US on a timeline in terms of protection.
With China the issue is different: They have a completely different military ecosystem so it's not like they can send them their own stuff. We already saw in Ukraine that running 2 types of equipment along each other is a pain in the ass and strains logistics. China is likely aiding them with satellite imagery instead.
I think China will sit this one out. There's nothing to gain for them with direct involvement.
Any assistance to Iran (like satellite imagery) will have limited effect, and the Chinese know it. In my opinion, there's no way the Islamic Republic survives this. For any rational international actor, there's no sense in becoming involved in a lost fight.