There's an article in this week's edition of LoL, but has been taken from Kalkan Turkish Local News (KTLN). They have tried to find out what is happening as the first of the 90 / 180 day visas are just expiring. They have contacted various authorities & about the only one that has replied is Dalaman Airport, who stated that you would be able to purchase a new visa, even if the previous one had not expired, (despite this being in contravention of the law).
However, if you were to overstay you would be fined & that you would have to buy your next visa before leaving your country of origin, at the Turkish Embassy / Consulate. Also, if you overstay by more than 15 days, you would be banned from reentering Turkey, for a period of at least 3 months rising to 6 months.
KTLN do state that this was the only reply they got, & that, of course it being Turkey, anything could actually happen