Turks; it will be the Turks. Never forget, the Turks are always and only about the Turks. Mohammedanism, for example, is just a tool for them. That’s all it ever was, except perhaps during the Kemalist era. But...if one understands what is going on, especially in the 21st century, this can be used to one’s advantage or the advantage of one’s own omogenia. For example, young Greeks are moving into Constantinople in substantial numbers and doing very well there by all accounts. They know what and who they are dealing with. Remember, the Phanariotes ran that empire for centuries. I expect that at least the educated population of the Arab world understands this. I doubt the peasantry, like Westerners, understand it one bit.
Most Turks around here are not very islamic. A few are Orthodox (not Greeks, but they call themselves Turks).
Turkey moving into a more leading role would not surprise me much. The only question is what will Iran do? They are not Arab, but Persian, and many of the people do not align with the rest of the ME. The leadership is set on agitation, but there are some signs that is changing.