Not necessarily. It could survive if the SNP were allowed to do pretty much what they want in Scotland in exchange for pretty much not interfering in rUK. It would work for both, given the SNP could play it to their electorate as 'you chose us over Labour, who then refused to go into a coalition with us... but by choosing the SNP, you're now getting our policies'. I'm not saying that's likely, but I wouldn't rule it out. There would have to be changes to how funding is affected in Scotland by changes to funding in England in certain areas, but that's not an insurmountable task.
You will say that wouldn't go down entirely well, but neither would 'vote SNP, get Ed Miliband... and no one in government'/potentially less positive change for Scotland than under a Tory government which lets the SNP do what it wants.
I'm really not sure you can say that with such certainty. Unless you know what's going on inside the top level meetings of the SNP and Tory party. See the rest of this post.