I'll switch when Swift is ready. Right now there are lots of bugs and odd issues even when you're using it as a scripting language (how do you import a framework?) and when I try to make something using a C API it ends up being an unmanageable mess of CUnsafeMutablePointers. I realize Swift will never be as good as ObjC at C interop, but it certainly doesn't have to be this hard. On top of that, the syntax highlighting and code completion in a code could use some work (!) and crashes every fifteen seconds (!!). So there aare definitely a few things that could be improved. It was released, like most Apple things, a year too early.
Please note that I am in no way biased or prejudiced against Swift—against my better judgement I was an early adopter and I saw it as something Cocoa really needed. I'm also disappointed it isn't and may never be open source.