"I wonder if that space will be occupied by new HD channels?"
In the past, they've only used F2 for HD signals. If there is actually 10 "spots" on F1 (I didn't see that many disappear, maybe you can remind us), they would have to move F2 programming to F1, which hasn't happened yet. Also, 10 SD channels mean 2-3 HD channels. Nothing to get too excited about, when there is already 10-15 more HD channels available. They really need 4-5 tps to be able to offer new HD without making some customers angry.
Currently, the last batch of HD additions has been toward english customers. In order to maintain the ratio, they need to add a french channel if they don't want to lose more customers to Videotron. But if they do, they will piss off english customers who just got "happy" to see The Frame showing up on their screen. I wouldn't want to be in SC's shoes to select which HD channel will be next.
With the limited amount of bandwith, the only thing they can add is pay channels content, which is what they did with those sports PPV/CI additions and Super Channel HD2. I suppose they hope to get more subscriptions to Super Channel package by doing so. Until they get the actual room, I expect the same kind of channels to appear.