If we believe the polls then there are two things Yes have in their favour.
1. These missing voters, hunch is mainly yes, not registered with polling companies. .. possibly 300k
2. Generalising slightly here... but all Yes voters will vote, not sure I can say same thing about No
Also, just to note, private polling on ground seems to favour Yes... and since there has been no real change in polls for c. 1 wk now, u could assume no change in ground... Therefore a Yes is still possible