I doubt would be short, that is the new frontier, if anything the balkans got muslim 800 years early now..that will be fun
I don’t think that Muslim states on the European mainland will be able to survive in the long term, simply because they will lack the hinterland, which will continue to attempt to push them out. The border between Christiandom and Dar al-Islam have been relative stable. The regions with steppe and desert hinterland have been able to push Christians out, while the regions with agricultural hinterland have been able to push Muslim out.
Of course that doesn’t mean that Muslim conquest won’t radical change Europe, the regions of Europe which fell to Islam was forever changed even after they were regained. Aa example if the Bulgar Empire is destroyed, it would leave the Romanians to consolidate and push south, or fleing Slavs overwhelm the Vlachs and Romania becomes Slavic. Arabs could be settled on the Danube frontier and later they’re reconquered and force converted leaving a people of Arabic speaking Christians running OTL Bulgaria.
But the biggest effect I think is that the fall of Constantinople only leave one Patriarchy in Christian territory; Rome. Which mean pretty much all conversion in Europe will be toward Catholicism.