Second in Quebec popular vote is the Liberals and I would think that most of the seats held by the Bloc currently would go to the Liberals, but of course I am guessing.
I'd say your guess is pretty good.
Despite the popular belief that the Bloc is a "single issue" party, they have a clear mandate on every major issue that voters care about and it just so happens that the Bloc is better aligned with Quebecers' generally left-leaning stance on major issues.
For example, Quebecers (and the Bloc) don't side with the conservatives on big issues such as Iraq, environment/Kyoto, young offenders, arts etc… On those issues, the Bloc's platform is much closer to the Liberals.
I'd say the only major platform agreement between the Bloc and conservatives is government decentralization: the conservatives are much less prone to meddling in provincial responsibilities, which Bloc voters tend to agree with.
Overall, on issues, I'd say Quebecers would more likely side with liberals than conservatives but the mistrust for liberals is still pretty strong so not sure every Bloc seat would go to liberals if Bloc wouldn't exist…