They do fly more than 500 miles regularly. Myrtle Beach is 700 miles and Halifax (they fly direct at times) is nearly 800. I think they're restricting the seats though.
With their hub at a non-jet location such as YTZ, I doubt they'd invest in any jets in the near future. It was probably just something that was said to detract attention. Instead, I suspect they'll wait until they have a second hub (possibly in Ottawa with their lounge and new routes from there), and then consider the possibility of become a national player.
While other airlines are trying to get into the airport, I suspect they'll do everything they can to max out their capacity of the airport, which they'll need more turbosprops for (their original aircraft order is nearly filled I think). AC must be a huge risk to Porter with their Aeroplan and business customers that are contracted to use them.