The only rumor I've seen is that AMD has a card coming with similar to GTX1080 performance.
GTX1080 is about 9TFlops (GTX1080Ti is about 35% faster potential), so a "25TFlop" card is pretty unlikely. It may be a compute card, but either way if it exists then it's got to be a DUAL-GPU card similar to a 2x GTX1080Ti.
Since I doubt we'd be hearing about such a card now it seems like a BS rumor to me.