Maybe, although I doubt it, but then if that is true, the left coaltion needs only two Arab votes to carry the day. They will get them, easily. There is a decisive majority for unilateral withdrawal. It will happen.
It's not about votes... it's about maintaining the coalition... and they cannot have Arab parties in the coalition.
I also think you're underestimating the difficulty of maintaining a coalition with far-left parties and religious and right-wing parties. United Torah Judaism and Meretz would not get along like the best of friends... nor would many members of Kadima (as some of them are still pretty far right).