I'd predict a 'No' vote by a majority of 10-15%.
Why? Well, the 'Yes' campaign is strongly emotional and very vocal, with words like, 'traitor', 'bully', 'day of reckoning', 'liars' and the like being bandied around, to the point where I think human nature causes some people to be put off openly declaring their opposition, or even debating the point, in favour of assent with the view of the herd, be it implied, muted or otherwise, when asked if they're voting 'Yes'. That's enough in my mind to skew the opinion polls which, for all their sophisticated methodology, have been spectacularly wrong in the recent past.
If I'm wrong and there is a 'Yes' vote, I'd be very sad but I'd then be pressing for Scotland to get what it's decided it wants - total independence. No pound, no shared Bank of England guarantees, no special treatment from the remainder of the UK and no going back.
As an Englishman (albeit with not-too-distant Scottish and Welsh ancestry) I'm deeply aggrieved that I didn't have a say in the possible dissolution of this union, which will affect my standard of living and that of my children and grandchildren for some years to come and for that I blame the abject weakness of the Westminster Parliament and the mind-boggling selfishness of the Scots leadership. A joint referendum could have incorporated a formula which allowed for the large disparity in population size, with a weighting being agreed (i.e. 1 Scottish vote = 1/x English, Welsh and Northern Irish ones) but no-one chose to explore it, That meant we, south of the border have been totally disenfranchised.
If the English had (say) suddenly decided to unilaterally ditch the Scots as some sort of encumbrance, in a one-sided vote designed to be hugely favourable to English aims, the Scots would have, quite rightly, howled with indignation and I would have supported their view 100%. As it is, if a majority of Scots turn out to care so little about me and mine, why should I do any differently for them?
Hopefully, come Friday the family spat will resolved in favour of unity but, even if it is a 'No' vote, I think that the wounds will not be allowed long to heal. And a small 'No' majority would, I fear, be the worst outcome of all.