Most likely yes. Anti-Papal sentiments had been growing for centuries, and the Black Death had wiped out much of the truly faithful of the clergy. The failure of the crusades hadn't helped, nor had the decline of the knightly orders. The Avignon Captivity was still a fresh wound on the church, and the burgeoning Italian economy was leading to ostentatious displays of grandeur even as the faithful starved. There were a lot of causes for the reformation, and the Ottomans were probably a pretty minor one in the grand scheme of things. Granted, the butterflies from this could make the reformation very different from OTL. If the Ottomans stop in Greece, that means that Hungary is still in play during the religious wars, which adds another Catholic power to the mix. And like you said, no Ottomans means the Austrians can focus on the Protestants instead. For that matter, Poland might be able to do something about them as well, though the butterflies could easily turn them to the Protestant camp. The most likely outcome of this is a defeat of Protestant political power in Europe. However, unless they're subjected to fullscale crusades like the Cathars were, they are going to stick around as a sizable minority. And by this point I don't think that there was much stomach for crusading- we've seen OTL how the Varna Crusade only attracted the nearby countries. Ultimately, you'd likely see a more heavily Catholic Europe with a heavier leaning towards Protestantism in the Americas.