I don't know what Russia will do about Venezuela, if they do, but they helped Assad a lot and this is why he was in his position for so many years, but Assad was making the decisions for himself and he made mistakes, like trying to reapproach the west after the arab states accepted Syria again after many years. That was a grave mistake.
Iran also preferes to stand to his own power because they afraid that if USA will make a very good offer to Russia,then Russia will have no other option to dump them (and Iran is right i think).
Hezbollah keeps very low profile but the weapons going for Hezbollah that had been recently confiscated by the terrorists that now govern Syria, show that a lot is going on in the background. We'll see...