It won't happen. At least, not in my lifetime. The majority of Scots supported devolution, however the number that support indepdence, which is a different thing entirely, is small. (My ICM/The Scotsman poll puts it at about 27% [Which tends to generally be the average and stays relatively static.] at February 2000. [Contrasting with 46% that wanted merely devolution.])
And even discussing any form of Welsh indepdance is purely academic.
So unless people forsee some great social upheval or turnaround in attitudes, then I can't envisage an indepdant Scotland at any time in the immediate future, so I'm not terribly sure what the 'They should and will become independent!' people are voting on the basis of.
Personally, I think the end of The Union, which is a completely artifical and bizzare creature, would be a good thing, and would give people a better sense of what their actual identity was, but that's a different thing entirely.