I got a correction email from Ilok today. They now officially support Mavericks. I haven't heard back from East West but none of my Complete Composer 2 instruments are properly licensed anymore and when I try to relicense the Authorization Wizard says the code is already in use. So Mavericks did something weird.
Ilok and East West Play instruments DO WORK on Mavericks! Despite what the error message was saying my instruments did not become unlicensed, all that was required was uninstalling and reinstalling Play. And as I said above, despite what ilok said yesterday, they do officially support Mavericks today.
It's working fine on my laptop. I haven't put it on my main studio mac because Avid is advising not to. PT doesn't support yet. I just got everything more or less working (Logic X still flaky with the Avid Core Audio Manager but launching it first seems to solve this) so I'm not looking to rock the boat yet.
Still, you gotta be careful. I tried downloading pages and Maveriks started to automatically download too. Now it's permanently paused.