I'm against packaging unstable stuff. We would be packaging a moving target where everything breaks every day. Let's not.
There's a reason there are stable releases (of anything): there's (supposed to be) a (social) guarantee that the API doesn't change in incompatible ways. If a library doesn't work in a stable release, upstream has to get it to work. Simple as that. Otherwise it just shouldn't be packaged. People can still use cargo to install it so we aren't preventing anyone from using it. That said, there could be a rustc-devel package (only for rustc). Other packages, people should be on their own. Please, let's not make unstable stable by decree. If anything, upstream should just release more stuff as stable (if it's stable) :P
