Really, I think they're all the same. They're all 'Chosen Ones' by some higher power or the other...Daedric princes...the Aedra, and so on...and, it's possible that the Nerevarine is still alive since they never die of disease AND age. If the Nerevarine survived the Oblivion Crisis (poor Saint Jiub) and the Dragon Crisis, he/she may as well be alive. Even if the Nerevarine didn't have the power to not die of old age, he/she could still be alive since in the canon since, Nerevarine was, by default, a Dark elf. They can live up to 300 years if they're lucky. Of course he/she would look like an old coot but that's beside the point. Plus, it's even suggested, according to the Elder Scrolls Wiki, that the Nerevarine made an expedition to Akavir and disappeared. So perhaps the Nerevarine is in Akavir doing who-knows-what.