Almost certainly not the final beta. The Swift language and its interoperability with APIs (Cocoa, Sprite Kit, etc.) still have a TON of issues, including some fairly major ones (and this is including the changes in this beta). They are making some progress, but there will be a few more betas, at least IMO.
They will make it final before the new iPhones ship. As for Swift, Apple has told developers to expect continual updates. I'm expecting iOS 8.1 late November or early September. Even then I wouldn't expect Swift to be 100% or even 90%.
----------
In the open source world Swift would be a 0.7 app. That is actually a good sign as it puts developers in the loop early. Frankly it isn't Apples intention to have Swift fully fleshed out until after at least a year and possibly two. They have been very clear about this.Yes, but all the Swift libraries get embedded in to the App package, so Swift can continue to evolve even after the 8.0 final release.