Rails 4.0 around the corner (opens in new tab)

Rails 4.0 drops support for Ruby 1.8.x which necessitates the major version bump.

From what it looks like to me, it's not so much about a drastic new feature set but rather about trimming down dramatically. You could argue that it really should be like 3.2 -> 3.3 similar to OSX Leopard -> OSX Snow Leopard. I think they gave it a full version upgrade because it WILL (not might) break a lot of apps. That's my interpretation. I might be wrong.

Ruby 1.9.3+ justifies the major version bump

Part of it could be PATCH replacing PUT.

yes, yes.

Aaron Patterson (tenderlove) gave a presentation where he said he wanted to refactor rack to make it more simple. He said Rails 3 had a lot more depth in the stack and it was making it slower. (when i start up an old rails 2 app i can't believe how fast it is). I don't think that is in Rails 4 though. I guess that is a separate project.

Also deprecating vendor/plugins means Heroku will have to change the way they deploy. You can notice that by the deprecation messages when you start a heroku console.