I know I'm a few days late to the discussion, but I just wanted to point out that Trudeau's comments aren't necessarily that bad for him. Assuming he wins (which seems pretty likely at this point, unless people like George Takach and Karen McCrimmon are secret charismatic dynamos), he'll get hammered for them in 2015, but I'm willing to bet that the Liberals will still pick up seats, in Quebec and elsewhere. The other parties will try to use it against him in the election after that (since I have to assume that unless the Liberals have truly lost their mind, they'll realize that they have to stick with a leader for more than 1 election at some point), but it'll be less potent, to the point of being dismissed as irrelevant by most people.
How do I know? Because Stephen Harper said far, far worse things about Canada before he became PM. He said that Canada is "a Northern European welfare state in the worst sense of the term" (in the U.S., to a room full of Republicans, if I'm not mistaken), and that it's a "second-tier socialist country". He also said that Atlantic Canada had a culture of defeat. They were all minor points against him in 2004, and then total non-issues for most people by 2006. It'll be the same thing by 2015, with the key difference being that Trudeau's thing is in French, which means it'll be a lot harder to use it against him in an attack ad -- and the people who will hold it against him probably weren't voting Liberal anyway.
(All that said, I have my doubts that Trudeau's Quebecois-ness will be the focus of Conservative attack ads anyway. I think they'll start out by just ignoring him, and then, if that doesn't work, they'll try and paint him as a lightweight.)
On top of all that, 3 years is a very long time. Who knows what the landscape will be like in 2015? Harper may or may not still be around, the economy may or may not have plunged or recovered, provincial premiers may either help or hinder their respective parties...we'll still have a massive deficit, because the Conservatives have zero idea about how to manage money, but beyond that, there are too many variables at play to say that the state of politics in November 2012 will remain constant until the next election.