Keithz and Enviro are having a good conversation, but I'm just going to chime in with some info that might help.
First of all, with regards to room on the Island, new hangars will probably be built on the south side of the airport. This should give them enough storage capacity to have 10 planes on the ground, if they keep a few planes at their gates, which they do. The issue is, whether they will have 10 places to keep their planes in other cities? I'm assuming they're being given a second gate at YOW, and maybe YUL, but that won't happen at any of the American locations, so they would need 6 locations where they would keep a plane overnight that aren't YOW or YUL. That means they'll need to find some new regular routes in the next year because there isn't the demand for multiple daily year-round flights to Quebec City, Halifax, Tremblant, etc...
Second, the ILS on the Island was recently updated around the New Year. This has made for a better situation than before, but at this time of year when fog is a big issue, you often get ceilings lower than 200 feet, and they aren't allowed to land at that threshold. With regards to using the second runway, they have never done this.
Third, Most of the people traveling on the YTZ-YHZ route via YOW, aren't the same demographic as those going to YOW or YUL. It's a lot of students and families who are just looking for the cheapest way to get there. So any route that involves a stopover somewhere (other than Tremblant which usually has a stopover in YUL) probably doesn't involve (m)any business travellers. So, let's say one day they felt Winnipeg would be a good destination with a stop in Thunder Bay along the way, it would probably consist of a different market that we don't normally associate with Porter, but has been growing steadily with these unplanned routes (Halifax was never in the business plan).
Fourth, I've seen images of the building (though this was last summer, and I don't remember significant details) and the floor plan/layout. It will be two floors, one for arrivals and one for departures. 5 new gates will be built as currently there are 5 gates, and these old ones will be recycled into the new structure, but improved to be include bridges.
Any questions or clarifications, just ask.