Normally, I pose these sorts of rumors as “Well, here you go, and here's a grain of salt.” This one I'm fairly sure is bogus, at least to some extent. I could be wrong, but especially the GP100 aspects of it just doesn't make sense.
Before I get to that, the rumor is that NVIDIA will announce a GeForce GTX Titan P at Gamescom in Germany. The event occurs mid-August (17th – 21st) and it has been basically Europe's E3 in terms of gaming announcements. It also overlaps with Europe's Game Developers Conference (GDC), which occurs in March for us. The rumor says that it will use GP100 (!?!) with either 12GB of VRAM, 16GB of VRAM, or two variants as we've seen with the Tesla P100 accelerator.
The rumor also acknowledges the previously rumored GP102 die, claims that it will be for the GTX 1080 Ti, and suggests that it will have up to 3840 CUDA cores. This is the same number of CUDA cores as the GP100, which is where I get confused. This would mean that NVIDIA made a special die, which other rumors claim is ~450mm2, for just the GeForce GTX 1080 Ti.
I mean, it's possible that NVIDIA would split the GTX 1080 Ti and the next Titan by similar gaming performance, just with better half- and double-precision performance and faster memory for GPGPU developers. That would be a very weird to me, though, developing two different GPU dies for the consumer market with probably the same gaming performance.
And they would be announcing the Titan P first???
The harder to yield one???
When the Tesla version isn't even expected until Q4???
I can see it happening, but I seriously doubt it. Something may be announced, but I'd have to believe it will be at least slightly different from the rumors that we are hearing now.