What Huhne should do now is become the leading voice in the party against going into coalition without a guarantee of PR. This would not be technically disloyal and Nick Clegg would be hard pressed to slap him down over it. But it would position Huhne perfectly if there’s a hung parliament. Clegg would be sorely tempted to accept an offer to go into government and if he did, Huhne could resign on principle.
The Lib Dem members would hate entering into a formal pact with another party and Huhne would be ready to move as soon as the coalition had to do something that seriously upset Lib Dem members. Considering how unprepared the membership is for the realities of government, it’s unlikely that Huhne would have long to wait.