If they use custom widgets, nothing Apple does will affect them. This is precisely why it doesn't matter whether or not developers have access to the new UI widgets, so long as common layouts are generally preserved. Anything using the default set will simply be updated to reflect the new look, just as a properly-styled website will when switching stylesheets.
Resolution independence requires all-new widgets. None of those have surfaced yet...so by that theory, resolution independence has been dropped from Leopard as well.
Of course they do. Why would there be different ones than used by the OS itself? Interface Builder provides access to the core components of the OS--they have to be created first, though.
Why? The developers are irrelevant. The large ones have the resources to update their applications almost immediately, and the small ones don't have prerelease software, so we'll be waiting months for those products either way.
The reality is that UI widgets are just about the easiest thing to change in software. They take a lot of time and effort to create, especially when you're doing a coordinated theme, but it's a simple resource swap in the end. You don't have to test it until the very end, so why release it before that? With just graphics designers working on it, there's a distinct Apple 'wow' effect when it's unveiled. We've been promised a new Finder, which so far doesn't exist at all; resolution independence certainly isn't finished, because almost none of the widgets scale properly; there have been ZERO changes to the appearance so far, which has never happened in a previous OS X release.
Something new is coming. It might not be the visage of God that some people seem to expect, but all the signs point in the right direction.
