It will slowly gain traction among iOS developers, and some will use it for new code, but that doesn't mean it will be dominant by any means.
I don't think you understand, for new projects it pretty much already is.
The fact remains that there are billions of lines of Objective-C code out there. If you honestly think that developers are going to rewrite all those billions of lines of code
Of course not but over time refactoring will rid you of much of that.
I'm not saying all of that is going to be re-written, but within a year I don't think many projects will be started that do not use Swift at the outset.
Now if Apple were to release an Objective-C to Swift translator,
In effect they already do by automatically generating Swift versions of any header files you want Swift to see. That means it's zero cost to call into any existing code from Swift.
If anything, they're usually not cynical enough to adequately model developer apathy and resistance to change..../em
You REALLY do not understand the iOS development community. I would agree with you in any other context, I have been a developer in a lot of worlds, from backend to front end dev. In any other community of developers you would be right; for iOS development you are so, so wrong - primarily because iOS developers are used to constant change anyway, the language changing is just one more change. If it makes you even a little more productive people will use it - and Swift does that quite well.
My predictions are also very, very conservative...