I don't think HYD needed the movie to boost the manga sales. That is the first new volume of HYD to be published in years, collecting the side stories that have come out since the main storyline ended. HYD has always been a great seller, I am sure it would have sold well anyway ^_^ Of course, the movie didn't hurt. :D
I picked up that volume last week, it's very nice! There are several cute color pages at the front.
This reminds me- now that HYD vol 37 is out, the separate entries for the side stories should probably be removed, if they haven't been already.