> That would be catastrophic to Israel: they could face Iran from the air and Arab ground forces from multiple directions. In fact there are already signs that Egypt is moving towards that, troops are moving in to the Sinai. There is a real chance that Israel could cease to exist.

Israel is a nuclear power, there is no conceivable scenario in which Israel would cease to exist that doesn't involve nuclear war. Israel also has a long history of defeating coordinated attacks from their neighbors with conventional means alone.