This is an extremely naive view of Scottish politics, and one that reeks of historical ignorance. As I've told you, Scotland has not always been a stronghold of the Left. If you look back to the early 90's you'll see the Tory's getting nearly as many votes as Labour. The fact it is dominated by Labour and the SNP today, does not mean it will be tomorrow.
Labour is currently polling ahead of the Conservatives, so if they won the next General Election your argument would be sunk, would it not? Scotland would have a Government which represented it's politics, which are apparently marginally left of centre. I say marginally, since Scotland voted New Labour which most Leftists don't even consider to BE leftist. The ACTUAL Leftists parties didn't even get a sniff at the elections.
You're trying to base the future of Scotland on an argument which hangs entirely upon the politics of the day, rather than any long-term view of things.