I think there will be time. There will probably be a period of testing, but you're right about the date. I think they will implement things slowly.
OH... how correct you are. See their latest blog post: sellingppp.com/blog So this could take some time to recoup any expenses incurred by those of us advertising this new program. Otherwise... still doesn't hurt anything to sign up and add the code to your pages now.
And us publishers are expected to add at least $3.50 additional income per every 1,000 visitors without have to use any addition web real estate