My own guess (without an evidence to back it up) is that the SNP's dominance will hold up pretty well during this parliament and they'll still win the vast bulk of Scottish seats at the next general election (probably over 40 of their current MP's being returned).
Once the Conservatives are returned for a third straight term at Westminster in 2020 though the desire to get the Tories out re-establishes itself and Labour make a strong comeback north of the border in time for the 2025 general election.
That presumes that they're isn't another independence referendum in the meantime and the Scots remain within the union.
Labour will win again once voters in England don't think they'll need to get in on the back of the SNP.
