Back in the 1970s Iran Air was a top level airline with a safety record at QANTAS level. There is a huge domestic market, a diaspora of Iranians throughout the world and major business opportunities as the country opens up after nearly forty years of sanctions.
Tehran is better positioned as a transit hub then the current bases of the ME3. Unfortunately with no alcohol available, a headscarf requirement for women and visa issues it will be more suited to origin/destination traffic, the more adventurous travellers or those seeking rock bottom prices rather than being a normal option like Emirates.
The next five years should be interesting.