Strictly speaking, the Nerevarine isn't immortal, at least not following the defeat of Dagoth-Ur (the prophesied Nerevarine couldn't fail), but because of his infection by the corprus disease "neither blight nor age shall harm him, and curse of flesh before him flies", he doesn't age. So assuming he didn't get his ass kicked somewhere, the Nerevarine is still alive and kicking 200 years later.

Also if you like magic, and are a member of the glorious PC master race, I highly recommend the Lost Spells and Apocalypse spell pack mods.