Since everyone else is talking about this, I suppose I must as well.
1) Anyone one seriously considering replacing Dion at this point is nutz. Who has the stomach for another leadership race? And in any case that would mean the Liberals abandoning their role of Opposition for another 6 months/ year while they wash their dirty laundry yet again, and Harper and Co., I don't know, fumble us into another war or decide to drill for oil underneath the Parliament buildings. Being on the opposition benches, opposing the government agenda, is still a job, and I don't think the Liberal Party will do itself any good by taking more time off work to navel gaze.
Besides, Iggy can get five days of negative media coverage meditating on Canadian wildlife. He is still NOT THE MAN. So Dion is there for at least one general election, and people in the party who do not want to spend another five years or so in the political wilderness should make peace with that fact.
2) In a week or two a new federal poll will come out, and (I wager) the parties will be pretty much where they have been: Libs and Tories within the margin of error, with (maybe) the Tories down a few points. People will forget the by-elections (if anyone outside the political nerdigentsia was paying attention in the first place), and life will go on.
3) Now, that said, there are problems in Quebec that may be difficult to fix. As KC at Scott's place wrote,
I do NOT want to be part of a party that advocates decentralism and special status if thats what it will take to become a serious contender in Quebec.
I don't either, but I am not sure what else the Liberal Party has to offer that they will be willing to buy in La Belle Province.