Oh a mahdi is coming back some day in the form of a God named Jesus Christ. Nothing Iran or the US or ISIS does will hasten or slow that day that will come. It is all God's time, His time is a day as a thousand years and a thousand years as a day.
Biblical prophecy has Damascus destroyed in a night and Egypt uninhabitable for 40 years. Those two events will happen before the Messiah returns, it may be decades away still.
There's no doubt that Christ will return...but I wouldn't refer to him as mahdi. I'm not advocating that Iran's actions will trigger their mahdi's return, I'm simply pointing out that they believe that it will.