Kadima has most to gain by this since they were going to get destroyed in the election. Labour are the biggest losers (maybe along with the Haredim) as they were up in the polls and would become the second party, and they might have to wait a year and a half.
Well, that's if you look VERY short-term. Longer term, though, Kadima is likely to be cannibalized by Likud and Labor (if you like the government, why not vote for Likud, which is determining its policies? If you hate the government, you should be voting for the opposition). Being in bed w/ Netaniyahu has done wonders for Barak's political prospects, hasn't it? Iz Mofaz seriously hoping to do better? More likely, he is simply going w/ his instincts and political preferences: and those are taking him to back to Likud.
This is the resumption of the normal service: the return of the sharonniks into the fold. Likud and Labor will be the beneficiaries: that's what is normal service in Israel, isn't it?