Soon (hopefully that was vague enough). According to DHH - "Rails 3 beta is almost ready for public testing. We're just hammering out the last bugs in Bundler. Stay tuned." [1].
As far as I can tell from watching commits/tweets/etc, the finishing touches are being put on now. It sounds like there is still some work to be done on Bundler as well as finishing up javascript handling. Other than that, I believe that all of the big pieces are in place and ready for a beta.
Hopefully someone on the core team who reads HN can chime in with a better response.
We've been putting on the finishing touches since the weekend. At the moment, we've been running through the startup experience over and over, clearing any rough bits that are low-hanging fruit.
We've been working on the new bundler, which makes the normal unbundled experience as safe and isolated using system gems (the "default" experience) as when you explicitly lock the dependencies. We cleared a bunch of small bugs today and are coming in for a landing.
