Obviously heavily-produced, heavily-designed graphic title sequences have been with us for quite a long time. But there has certainly been an upsurge of post-film credits sequences with flashy visuals in the last decade or so.
For example, Pacific Rim: https://www.youtube.com/watch?v=2oYcfPAjSzE
Or this one from the Seth Rogen The Interview: https://www.youtube.com/watch?v=vQp3rRdPGOc
Or from the genre I most associate with this, Motherfucking Marvel Movies: https://www.youtube.com/watch?v=Ui0AHvSzkH8
They often seem to showcase 3D models from effects sequences. Or, in the case of The Interview, a playful engagement with some feature of the movie's world or thematic concerns--here being North Korean propoganda--mixed with some things that are slightly relevant to particular scenes in the movie maybe.