Well, I can't say for certain, not having had the opportunity to test these new machines, but my guess is that since Mac OS X itself relies on a variant of BootX, the normal BootX will still be usable. I think when they say that the new machines won't boot OS 9, they probably mean that they won't be creating Mac OS 9 ROM support for that hardware, not that they'll be changing the machine such as to lock it into OS X.
tooki