Yes, it absolutely would. Between the locals, specialties, ethnic and PPV channels, you're probably at around 300 some odd channels. That is a lot of bandwidth free'd up. Yes, some of that will be replaced with HD equivalents but for all the SD channels that remain, you could probably fit them on 2 transponders using MPEG-4 compression and 8PSK Turbo modulation. Plus there is still a bunch of transponders on Nimiq 4 that could fit another HD channel or two. If you look at the traffic plan on Nimiq 4, 31 of the 32 transponders is used for SD channels. If you drop all the channels that are already in HD, convert the remaining to MPEG-4 HD or SD, you'd have at least 10x transponders remaining. As an example Shaw Direct is using 4 on F1, 22 on F2 and 16 on G1 for a total of 42 transponders. Bell is using 64 in their current configuration. Even with all the ethnic and small community channels that Shaw doesn't carry, most of those would be MPEG-4 SD and would fit on one transponder.
I don't know what's going on with the Satellite division these days. It's been years since they released a new receiver. They may be holding off on the MPEG-2 decommission because they don't have enough stock to replace all the MPEG-2 hardware that's out there. My guess is whatever receivers they are using today are not being manufactured anymore.