These are not going to be available in sidebar ads, only boosted Page posts at this time.
For those who don’t like the idea of animated GIFs cluttering up ads on Facebook, there is hope.
Facebook tells me “GIFs can be a fun and compelling way to communicate, so we’ve started testing GIF support in posts and boosted posts for a small percentage of Facebook Pages. We will evaluate whether it drives a great experience for people before rolling it out to more Pages.”
So if users hate them, we might not see them roll out more. That said, if advertisers love them – especially if they are willing to pay a premium to use an animated GIF – we could see the test become permanent for all Pages.