That's a good question. One in which I have thought about too. There's a reason why Russia has a naval port and an AF base in Syria. There exists a defense pact with Moscow. The answer is most likely Russia will enter the fray only after every means of peace talks fail. Right now, Moscow is most likely coordinating with other governments to pressure Israel into peace talks and also lining up governments that will stop Israel from further land grabs. Everyone knows Jordan and Iraq are next after Gaza and the West Bank, Syria and Lebanon.