Although there is room for a runway extension, is there any need for one? It's not like we get flights every day using the whole runway. Admittedly some of the recent flights to Calgary have gone via other places (Some Arkefly flights when full have gone via Keflavik. Altho having said that the nearly empty ones have gone direct).
As for the parallel taxiway, I think its due to the fact Bravo needs rebuilding, but without that we could not handle 737's as the Alpha taxiway is too small/soft and Charlie/Delta can just handle them. Therefore before you can rebuild Bravo you'll need another taxiway to handle the larger jets (eg Onur's A321's) so I guess thats the thought behind the parallel taxiway?!