Which (if any) party leader would resign after the Canadian federal election?

Dion resigned.

Dion has resigned, though it will only become effective in May when the Liberals have their leadership convention.

Dion has just announced that he will step down as Liberal leader. He will stay as the leader until the next leadership convention to assist the transition process.

Dion is calling for a press conference on Monday. It is expected the party has convinced him to step down.

none will resign.

I think only a leader who is expected to "win" (be that the actual election, or gain a certain number of seats) but fail to live up to that expectation would face serious pressure to resign. That eliminates all the leaders except Harper and Dion. I personally feel Harper can still win a majority (though it will be a very slim one, if even that), so the pressure is on Dion.

Many Liberals did not like Dion to begin with, and his leadership was questionable during the last Harper mandate, so if the Liberals cannot win (which I don't think they will), or worse yet, lose to the Conservatives in Quebec, there will be immense pressure for Dion to step down.