UKIP's fortunes are indeed the wake-up call to which I was referring. It rather relies on enough voters sticking with them at the election, rather than returning, defeated by the system but otherwise silent about it, to the two (or three) main parties, though -- and then, for these voters to still not be enough to lead to any (or no more than a handful of) MPs.
And then on the other side, if the SNP start picking up a huge number of seats on a tiny vote share, then perhaps the right should take notice of that too.
If instead UKIP voters give up, and return to the Tory party etc, then there's any hope of making this an issue gone for another election cycle at least. Even optimistically I wasn't necessarily expecting change any time soon -- just that more people might start to take notice of how bad things actually are.
But as long as the Conservatives and Labour continue to hold, say, over two-thirds of the vote between then, and if the various constituency results aren't quite as tight as they could be, then it is easy for this issue to be swept under the carpet. I'm really hoping that UKIP can get at least 17% of the vote share nationally (or at least in England and Wales), because almost certainly this will still not lead to many seats. And, well, people should be angry about that. They should be angry about it now, for that matter, if people are intimidated by the "inevitable" failure of UKIP at the polls and feel compelled to vote for the two main parties.
We'll see what happens in May, of course. So long as UKIP do well enough that they should matter at Parliament but don't, and so long as the SNP don't do well enough to matter but do, I'm predicting a wake-up call.