What I believe they mean is something like a second demo.
Now, what this "second demo" could do is incorporate The ones in the current demo, while adding perhaps... 3 to 7 characters. Now, the only way I could see this happening is sometime after a certain amount of these demonstration videos are shown.
The demo would include the original 14 from the demo's first release, as well as whatever ones they've finished the demonstration videos for. This would, therefore, be showing no new characters that they're still working on.
Now, you'll probably be saying "They're probably still WORKING on these ones, hence why it says 'May change' in the videos' openings". While yes, this is true, they could focus their attention on the additions for the demo's second release, so it can be given to tide over the fans.
Now, even if they don't do this and wait for a full release, I will stand by and wait. This is probably my most favorite mod to date for Brawl by far, and I will gladly wait for the entire thing to be completed. However, I know not all fans are like this.