I completely agree with this. We (bugsnag) are running on rails 4 beta right now to help iron out any production issues before that is released.
We didn't, however, realize that "patch" releases also have release candidates. I'd recommend following the rails blog (http://weblog.rubyonrails.org/) which announces release candidate builds too.
Ok, yes, that's an extremely great and open-source way to handle this.
But seriously, can we at least expect moderately stable releases? I do not think that's too much to ask, especially for a framework which has, in the past, achieved that.