Here's the salient points lifted from that post on a different forum - so everyone can be on the same page.
...let me tell you what I know. I'm not a coder. I'm a pro audio editor and writer. In fact, my most recent gig was editing the Keymap 1.5 manual, which features tight integration with the Logic 8 EXS. This required the direct programming work of both Redmatica and Apple. So here's what I know. And this comes from discussions with 3rd party developers, and developers with Apple.
The audio engine of the EXS is compiled and runs as a 64-bit process. This means that it can access more than 4GB of RAM.
This is a significant feature of Logic Pro 8 and they're quite motivated to make sure it works.
And there's even more fun and exciting news:it is now possible for third party AU plug-ins to do the same thing in Logic 8! In other words, a third party plug-in, such as Kontakt, can develop a separate 64-bit executable for it's audio engine, and then it too will be able to access more than 4GB RAM from within Logic. Now, I'm sure this would be a LOT of work, so I wouldn't expect it to happen soon, if at all. But 3rd party developers have recently been seeded with developers copies of Logic 8, so you can start harassing all of them to rewrite their plug-in to include a separate 64-bit executable audio engine.
What I believe is that we're currently seeing the best of all worlds—64-bit addressing for samplers without all the detrimental aspects of a fully 64-bit application (lack of 3rd party AUs available, GUI half the speed, half the track count, etc). Good times for Logic!
Orren