I personally don’t know how Apple is going to do this, but they are trying to patent the technique as its own. On the other hand, I hope they adopt this cool feature to Panther OS X 10.3
“Apple has filed for a patent that suggests the company is working on a new mobile device capable of supporting multiple users. Either that or it’s cunningly trying to outflank Microsoft’s lead on fast multi-user switching by retrospectively patenting the technique as its own.
Almost as interesting as the patent’s content is the name of its lead inventor: Steve Capps, erstwhile Mac OS Finder co-designer and more recently Microsoft’s Windows UI architect. Capps is also remembered as the designer of the UI used in Apple’s Newton PDA. That gives you an idea of the application’s heritage”
Just because it sounds like you weren’t sure, I just thought I’d mention that this is confirmed for 10.3.
http://www.apple.com/macosx/panther/fast_user_switching.html