For fulldive vr, at least the type of fulldive this sub envisions, we would need BCIs that can not only read the brain, which already exist, but also write to the brain as well, and as far as I am aware, these do not exist as of yet.

I would be more confident in making any kind of prediction if we hade some kind of rudimentary interfaces that could do so, but as it stands now I think FDVR is a ways out yet.