Just logged into our SSP account and we're getting billed for January clicks. It'll probably be gradual. Last year our SSP contract expired and our pages were removed from the system, but we didn't see any traffic loss for almost a week. Ultimately it took the system 10 days to completely remove all our pages.
Yahoo paid inclusion is still live. Our rep said they were extending it for at least another week. I think it's tough for them to part with that revenue so I wouldn't be surprised if it continues through Jan.