DaughterDilemma - of course there's the possibility technically of Scotland rejoining the UK or joining up with other countries, but the point is, it isn't something Scotland gets to decide by itself at that point. Right now, Scotland has a pretty good 'deal' in the union, in terms of how much money it gets per head, how much devolved powers it has and how many independent systems/instiutions (NHS, education, legal etc), and a lot of control on how they are run. If Scotland leaves and then wants to rejoin the UK, it won't be Scotland who are setting the terms and it's unlikely the rest of the UK would consider it to be a good enough deal to them to agree to it.
Let's face it, if it's all the land of milk and honey the Yes campaign are saying it will be, they wouldn't want to rejoin. A public/political will to rejoin would only be if it went seriously tits up, and why would the rest of the UK, or any other country, want to take that on unless there was something in it for them?
This is a one way deal. If Scotland goes alone, it stands or falls alone. There's no "let's just try it and then go back to how things are if we don't like it" option. That was a possibilty with devolution or devomax, but not independence.
Saying "nothing is forever" is wrong, this would be. So it's important that people are 100% aware of the probable downsides (even if just in the short term) of those choices.
As I said, I think long term Scotland would be OK, it's never going to be a super power, or particularly rich unless it goes the tax haven route (which there doesn't seem to be the political will for), but it'll be OK, it's just stuff like banks and major companies shifting out (either completely or just scaling down in Scotland) for the first 5 or so years while things settle down, are predictable and should be planned for, not denied.