OK, imagine the situation a few years hence. Labour are in running the country in a minority government where they have a similar supply and confidence deal with the SNP to the one the Tories had with the DUP. Not exactly that far fetched a situation, I don't think. The Labour government isn't getting instant results at sorting out the mess the Tories left the UK in.
The Tories then realise that Scotland is lost to them (because it is), so they offer the SNP a binding referendum if they'll vote with them in a VONC. (The Tories have form for this too)
Which way do the SNP go?
I know where I'd put my money.
Just like the Liberals / LibDems would sell their own children for the mearest sniff of power (thats been the Lib way as long as I've had an interest in politics) the SNP would do the same, I have no doubt. Scottish Independence is what they want and that is fair enough but they'll go with anything they think can deliver that.
And I genuinely do think once they'd achieved it, they would implode
I don't think any of the main Parties have changed their spots much in the last 50 years
Tories - just being Tories but more extreme as time goes on
Labour - riven by infighting and only ever stand a chance of being elected when the centrists can subdue the left to the point of irrelevance
Libs - the sniffers of the knickers of power.
SNP - sell their soul to the devil for independence
That has been the way for 50 years and isn't showing any signs of changing