It wouldn't surprise me if turn-out was very low as more and more people are peed off with the MPs who are only out to line their own pockets with no regard to helping their constituents.
I'm holding off betting on the turnout this time round.
Whilst many people remain very angry (although many still seem to think their own constituency MP does a good job, its just the others who are on the take), I don't think it is clear cut what form their anger will take: will it be apathy, or will it be an explosion in voting for smaller parties/independents? Might UKIP, Veritas and the BNP do much better (even though their elected representatives have an even worse record of expenses fraud!) and maybe the Greens and Socialists, depending on the constituency. Might there be more independents standing on anti-corruption Martin Bell style tickets? The Jury Team is an interesting development, that could gain traction and votes.
There's also the the Presidential style debates to consider between the main parties' leaders. This might have a positive impact on voting turnout.
I wouldn't be surprised if turnout dropped, but I wouldn't be surprised if it increased either. Therefore I'm keeping well away from the betting markets on this one.