You can already upload GIFs as your profile pics and they can be animated, though I believe the file has to be 50kb or less.
To see the animation you have to head to your profile, then open their avatar in a new tab. You'll see the GIF animating if you do.
I'll keep my profile pic as a GIF for a while if you wanna check it out. Just visit my profile and open my avatar in a new tab and you'll see Sakura winking at you~