I dont wanna defend Hearn but without him there couldnt have been Joshua vs Ruiz and everybody knows how much him and Joshua risked with those fights.
I doubt they'd leave the annoucement to Pulev so I imagine the fight taking place in İstanbul is merely Pulev's expectation. The suggested venue, Besiktas stadium (Vodafone Arena), is a beautiful football stadium right on the coast of bosphorus. https://i.pinimg.com/originals/7f/3d/d4/7f3dd4a1ffa988bb853195d5d5c02baf.jpg For football events it hosts around 42,000 people. For boxing I imagine the capacity can extend to 60k+. If the fight actually takes place in Istanbul, I'll be there.