I think a minority is definitely the most likely outcome here, with a majority on either side being highly unlikely but conceivable. If Dion and the Bloc both run an abysmal campaign, Harper would have a chance. He'd have to make major gains in Quebec, defend his gains in Ontario, and win additional seats here too. That's a pretty tall order, especially when considering his lack of policies to attract urban and suburban Ontario voters.
Interestingly enough,
the most recent polls show the Liberals at 50%, which is about what they were at during the Chretien years when they won every seat. Most of those votes are coming from the NDP, which couuld swing a huge number of ridings away from the Conservatives through reduced vote splitting. I don't think 90s-style sweeps are in the cards, mind you, but the Liberals could make significant gains. Right now, the Liberals and Tories are more-or-less tied in the polls, in the low 30s. Unfortunately for the Tories, their declines have been disproportionately in Ontario. They're retaining their supermajorities in Alberta, but many seats over here could be at risk. Their rise in Quebec also seems to be stalled.
If you plug the most recent couple polls (Nanos, Harris/Decima) into the Election Forecaster, you get some pretty interesting results. Major gains for the Liberals in B.C. and Ontario, minor gains for the Tories and Liberals in Quebec, and minor gains for the Tories on the Praries (there's not much more for them to gain!). It projects, from the raw numbers, a total wipeout for the NDP in Ontario, but that's certainly not going to happen. That may be even worse news for the Tories: contrary to the NDP's rationalizations behind disappointing results in the 2004 election, people in Downtown Toronto ridings are smart enough to know they don't have to vote strategically since the Tories have no chance. That means that most of the NDP voters in Downtown Toronto and the other NDP seats will remain NDP, while a lot of NDP voters in no-hope suburban, rural, and mid-sized city seats are swinging to the Liberals in order to defeat Harper.