I haven’t even figured out Rails 2.0 yet and Rails 4.0: Beta 1 has been released!
Lots of changes here, hit the page for more details.
The purpose of this beta is to get as many people as possible to try to upgrade from Rails 3.2 and earlier and to get an adventurous few to start new applications directly on Rails 4.0. That’s the only way we’re going to suss out all the issues and ensure that we can launch a solid final release. So please help us with that if you can!