Can the left gain the upper hand in the European Parliament?

I mentioned the European elections in my previous post, and it was interesting to see William Hague on Newsnight confirm that it is still the Conservatives' intention to withdraw from the EPP-ED group after the June poll. Paxman seemed sceptical, but Hague left himself so little wiggle-room I tend to believe him. I suppose that should be my cue to go into a rant about the Tories drifting off to the lunatic fringe of hard right, Europhobic politics, but I'll leave that to others. What intrigues me is whether the loss of the EPP's British, Czech and presumably other associates will lead to the group surrendering its decade-long primacy in the European Parliament to the Socialists? I don't really know the answer - you'd need a labyrinthine spreadsheet of opinion polls and trends from 27 different countries to know how the groups are likely to fare across Europe as a whole, but it must at least be a possibility.