I mean, if we think about it in the base game we've already had potential references to the CoC which wasn't that long after the Nerevarine's time, let alone the heavy involvement they had on the island.
Moreover, we've already seen one of the main artifacts the Nervarine required in Morrowind.
Spoiler
Specifically Keening
During the base game. Now if we take that, coupled with the heavy Dunmer influence/population on Solstheim following the Red Year, it seems likely we are gong to get something involving the Nerevarine even if it's just a reference. I find it hard to believe nothing of him/her survived the Red Year, yet alone the involvement on the island during Bloodmoon.
Now, granted, I know that the rumors started the Nerevarine went to Akavir after the events of Morrowind, but is it really completely likely that all traces got obliterated in the years in between, let alone when some Dunmer are capable of being alive 200 years ago and surviving into the present day?
Different line of thought then we've been thinking about I know, but I just keep thinking about any references or things this may bring to light.