This thing can go on for years. Or it could collapse tomorrow. Insurgent movements have been defeated in the past. Iran is good at crushing internal opposition. Will they be able to do so inside Syria? Well, they sure raised nine kinds of hell during our involvement in Iraq. 'Stan as well.
I would have thought the Gulf States would have stepped up to the plate by now. More active. But time will tell...
Russia cant afford to back Assad for long.
Its not the Soviet Union. They don’t have money to burn, and ports outside Russia are moot when the Russian fleet barely exists, particularly in the Black Sea/Med. Nice to have, not have to have.
Anything can happen of course. The Iraq precedent is instructive. Its way more expensive to suppress an insurgency than it is to keep one going. I am sure the Saudi and Gulf money is flowing in this proxy war.