This is in and of itself an incredibly difficult question to answer. it really depends on the situation of its salvation, and how it remains intact. Does this Crusader state remain unitary? Does it remain divided into petty fiefdoms? How strong are the foreign powers likely to intervene, both Arab, Persian, Mongol, French, Roman, and Holy Roman? Etc, etc.
Now, the Crusader states if they do survive will be the focus of petty politics, and their borders will recede and diminish overtime, with the northern counties being taken under Roman influence at times, while Jerusalem itself could come under Egyptian influence time and time again.
Once established, you are likely to have ongoing contact with the Italian Merchants. This won't necessarily lead to settlement, but the establishment of small Italian communities on the coast alongside the valuable waystations. You'll likely have Frankish and German immigration trickle in, with wayward sons attempting to make a name for themselves in the kingdom - and the various kingdoms going out of their way to bring the rich kingdom and its counties into alliance with each other.
Let's not mentioned the continued patronage of the Romans, so you'll have Greek competing as well, especially in the northern cities. Armenian might also become a common language in Edessa and similar northern counties, with Cilician Armenia remaining a major neighboring state.
So, by the 1600s, you'd have an utter mess. Multitudes of various small European-language enclaves would dot the coast and the major cities. Italian (Venetian, Genoese, maybe Pisan even), French (d'oil & d'oc), German, Greek, Armenian, and etc. A pidgin language would likely emerge as a trade language would form. This would be your proto-Maltese Franco-Arab tongue, which I'll just call Crusader for lack of a better word. This would exist along the major trade routes and the larger cities, though Arabic would be a larger tongue at first, eventually fading over to the pidgin form. On top of that, you have the Assyrian/Chaldean/other enclaves dotting the region, making the entire Levant a true patchwork.
Now, as for religion, it would be a slow conversion, but with the Crusader states well secured enough to survive permanently, they'll also be strong enough to encourage conversions. Some will happen naturally just to be more successful in moving through the government and gaining access to certain positions. A trickle of Europeans will come in over the centuries, boosting Christian population, especially in the cities where they will congregate, which will create a very mixed environment - urban Christian vs native Muslim and Christian populations.
This is all just conjecture, mind, but I don't see anything being nice and neat.