Not true. They are scarce and have suffered much persecution, but they still hold on. About 75,000 live around Yazd and in a few other places in Iran. This is not a whole lot less than the number in India (about 150,000), although in India they are a wealthy and influential group.
Oops, when I made my post, I said to myself 'not one left', and answered myself (I am a great self-conversationalist you see), 'nah, that crowd could never have left one alive'. Just goes to show you, try to avoid absolutes in statistics. Those Zoroastrians in Iran must be one tough bunch, to have held on this last nearly 1400 years of savage persecution, I wouldn't want to mess with them. Their burial practices still are unlikely to win them many 'good neighbor' awards, I'll wager.