It looks like they've just taken the release that we've already had (4.0.249.30) and made it more public. If you've already had the developer channel build, then you've already got it. Please correct me if I'm wrong.
If you're on the developer channel you'll continue to be on the developer channel. That is, eventually a stable 4.0 release will happen, but because you're on the dev channel you'll be updated to an unstable 5.X beta.
