The next few weeks are unpredictable; there's a report that Iran will close the Strait of Hormuz, depriving some countries of precious oil coming from oil-rich regions.
The world is watching, countries allied to Iran will first think of economic repercussions in their country before they will go to war.
In the last world war, we did not have the United Nations; so the WW2 happened, and the UN will play a crucial role in appeasing tensions leading to WW3.
The world has learned from WW2, and that bitter lesson will give a second thought for many nations to ally themselves with countries in an ongoing war.