The last animal was on-exhibit when I visited. I know Tanganyika imported a troop from Europe some years back that has since grown significantly. They've dispersed some animals to other non-AZA institutions, but are theoretically a source of additional animals for Bronx. That said, I expect the zoo will phase-out the species once their last individual dies. There's already a breeding program for them in Europe and US zoos aren't exactly lining up to take on additional primate programs. The black morph animals also look pretty much identical to the Silvered Leaf Monkeys elsewhere in JungleWorld.
I agree that Crab-Eating Macaques would make for the most suitable replacement, however I expect it is much more likely that the zoo obtains Francois' Langur given that they're an AZA managed species. Time will tell I suppose.
~Thylo