While Johan did not specifically say that we are looking at Fiji-based flagship, he did comment on his Twitter account that "this new island is one seriously impressive and sweet GPU," and that it will be put to good use, most likely on Star Wars: Battlefront game which is developed on Frostbite 3 engine.
While the angle of the photo is just right so we can't see any important details regarding the new graphics card, it appears shorter than usual flagship graphics cards, as expected due to the use of High Bandwidth Memory (HBM).
It also appears that we are looking at the liquid cooled version of the Fiji GPU based flagship. Unfortunately, we can't say much more about it as we are not even sure if it is a liquid cooled version since we do not see any pipes or radiators on that picture.
AMD was certainly involved with this "leak" and we are quite sure we will hear more about it in the coming weeks as we draw closer to the rumored June 16th launch date.