This, actually, is not true. The side NPCs during the Ivalice raids have a lot to say about the culture of the Viera, and it's mentioned that more and more Viera have been leaving the wood in recent generations, to the point where they're not an uncommon sight in the cities of the area.
Canonically, your Viera is NOT the only one to have ventured out of the wood. There are plenty.
Now, if I remember correctly, it IS the case that it's mentioned that those that leave the wood are forbidden to return. If an expansion actually has the WoL interacting with the Viera of the Green Word, that could cause some awkwardness. Perhaps SE will soften the "forbidden to return" bit, and just treat the WoL as though they've been unpersoned. They would be regarded as an outsider and a stranger and are treated accordingly - which, as it happens, is also how they'd treat any other race.
What??? I barely know you! Why would I...oh, you meant "Bear with me". Whoops!
