Hello Wulf,
There will be some sort of addendum stating that Mind Flayers are the IP of WOTC and used with their express permission.
Now, I believe that all the Feats, PClasses, spells, Psionic items, the Flesh-Craft skill and Flesh-Crafted Items, etc will be Open.
What we (PCI) plan to do is swap out our own replacement for our friendly Calamari-faced villains (We call them the Voiceless Ones) and proceed as best we can with future products.
We've had plans for Mind Flayers in our Arcanis world setting and hoped to use all the material from Unveiled Masters to support it.
Obviously, we now can't without a bit of creative tweaking.
But that's fine. We view this as an opportunity to make Arcanis even more unique and intersting.
I guess I've rambled off the subject and have probably given you more info than what you were looking for.
Bottom line, there's ALOT in the book that should be OGL even after the SRD finalization.
Best,