A large shoe which Apple will drop is, of course, virtualization. Virtualization will tie in with a recent Apple patent which, linked to the TPM chip, will allow the new machines to run other OSes inside a sandboxed “virtual machine”. Those other OSes will believe they have a somewhat slower system all to themselves, while running inside a separate window (and, perhaps, disk partition or disk image).
Putting this together with the previously discussed flash memory hypothesis, the advantages to Apple become obvious. Why should they need to have a standard BIOS or EFI at all? They can boot directly into the virtualization kernel (or whatever it’s called at the moment), from encrypted flash memory, which in turn would run a subset of Mac OS X – perhaps only the kernel with drivers and the windows manager – to have a basic GUI to check out which virtual OSes the user wants to run. This could be a full version of Mac OS X, or any version of Windows, Unix or Linux that runs on the abstracted hardware presented by the virtualizer.
In fact, it seems that a virtual OS could be a stripped-down OS specialized for a single application – something like what’s used now for embedded systems. It might be a gaming OS optimized for full-screen interfaces, for instance, or a TiVo-like appliance, or a multimedia center.
So, Apple doesn’t have to tie itself to standards during the boot process; in fact, this means that even if the user wants to run some non-Apple OS most of the time, the Mac interface will be present all the time underneath. At the very least, you can imagine the current ghastly BIOS user interface neatly presented in Aqua…