I think MANY people were NOT expecting this to happen (it still might NOT). It certainly is taking me by surprise, as I was NOT expecting it to happen.
So if this is really going to happen, then there appear to be a number of major issues, which although they would primarily affect Scotland, in practice, I would expect them to bite back, and affect England and the rest of the UK directly/indirectly for various reasons.
This could end up being a big disaster, for Scotland/England and the rest of the UK.
The problem is, if Scotland was suffering badly over this, I can imagine various ways, in which that would impact the rest of the UK.