A pretty sure that Windows 10 video will be released well before they push out Insider/Developer preview build becoz:
1. These Word are from MS's VP and he himself gave a deadline so it will released soon.
2. They didn't gave any dates for their build released =>we can/cannot expect any time soon.
3. Releasing a hair rising video about their new Os will give more media attention and will also sway more users to test their preview builds.