Well, Islam probably wouldn't make it very far into the east; it might make it into Anatolia during the Turkish Wars, but no further. However, if history followed the same pattern as it did here, they might make it into Greece, while western Europe would reform into powerful states. I mean, I live in Aachen, the place where Magnus the Frank ruled until his death caused the capital to revert back to Rome, and there's still a lot of Muslims left over from the Moorish invasions a millenia ago. Would the same thing happen in, say, Epirus?