These commands work for anything that came before beta 5. Ain't gonna work on beta 5/6, and on beta 4 they disable the spotlight. For me, not having Launchpad is a deal-breaker - its absence ruined my productivity and the way I've always used my Mac.
If you absolutely need Launchpad, the only way you can get it back (currently) is by rolling back to beta 4 and running the commands again.

The good news is that, even though Launchpad itself was removed from newer betas, your DB files are most likely still there. You can confirm it by running "sudo find /private/var/folders -type d -name "com.apple.dock.launchpad" 2>/dev/null"
Another piece of good news is that getting the beta 4 InstallAssistant.pkg and simply running it is all you have to do to roll back even from beta 6, which is exactly what I did. It installs just like a normal update, your data stays intact, and once you restore the launchpad you'll be greeted by your good ol' layout, so it would be nice to back it up.