When the IDF calls up its reserves and puts its ships in the Persian Gulf, then is the real time for worry. Right now, only the US and UK are sailing in Harm's Way. Wars might be started by air power, but they are won or lost on the ground. So far Israel is only threatening to start something it expects somebody else to finish.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: Israeli warnings on Iran war are more than empty threats