I think this is a storm in a teacup. In Scotland the super-majority is 66%. If you are serious about fixed term parliaments you have to have a super majority.
It still would only require a majority of parliament to change this rule back, it is not a democratic threat. This is all a bit of a red herring.
As it happens I have always thought the idea of fixed term parliaments (that loads of people were weirdly raving about before the election) a waste of time, because if the government of the day wants to find a way to call an early election they usually engineer a confidence vote and lose it. This has happened in Germany where they have fixed terms. There has to be this election escape clause otherwise you could end up with no government and years till an election.
I am beginning to think the Tory banckbenches are going to use this to scupper the coalition deal. We could be heading for another election within months unless the Lib Dems back down.