I'd say these two rumoured/confirmed x70 and x80 GPU are pointless at this point and very limited once again, because nVidia knows just how much everyone is eager to get one of them. It'll be selling really well anyway. In the last gen (Maxwell), the fastest affordable GPU was GTX 980 Ti - had 6 GB VRAM, however the GTX 980 for laptops (not Mobile version) already had full 8 GB of VRAM and in tests it performed a few frames better than GTX 980 (desktop).
We all know that the Pascal can have up to 32 GB VRAM, but if they are planning to use only 8 GBs at launch, it's pointless. In this case, if it would become the truth, the x80 Ti would have 16 GB of VRAM and the new Titan - 32 GBs in Q1, 2017, because the generation will end in 2018, so they need to get everything from the Pascal before then. But the gap between x80 - Ti - Titan would be too wide, especially if they would utilise HBM 2 as well. So could it be that Nvidia is trying to change their marketing strategy on desktops this time around and introduce even more versions of graphics cards just like what they've done with mobile GPUs in the past? If we put the new Ti version as x90, then it could be as follows:
x60 - 6 GB GDDR5
x70 - 8 GB GDDR5
x80 - 8 GB GDDR5X
x85 - 12 GB GDDR5X/HBM 2
x90 - 16 GB HBM 2
Titan - 32 GB HBM 2
It looks pointless doesn't it? In this case, I'd say those "confirmed rumours" might still be wrong and we'll see something like:
x70 - 8 GB GDDR5
x80 - 12 or 16 GD GDDR5X
x80 Ti - 24 GB HBM 2
Titan - 32 GB HBM 2
There is still a possibility that we won't get 32 GB VRAM at all, because nVidia might want to drag it to next the generation after Pascal, but it should hit them quite hard, because they've promised those 32 GB VRAM capabilities to their customers.