The 3080 has the same number of cuda cores as the 2080ti, and we know there will be IPC improvement, so the 3080 will be faster in rasterized graphics. Rumors indicate it will crush a 2080ti in raytracing which is where Nvidia's focus is now, and it has 25% more memory than a 2080. How does that sound like a xx70?
Yes, I am aware of all that, and hopefully it is even better, but usually xx80 and xx70 were the first two to be introduced. It used to be a midrange chip, and a slightly cut down midrange chip, which would then be marketed by Nvidia as high-end. If these rumours are correct, this time they are also introducing a midrange chip and its slightly cut down version, but with different names. Number of CUDA cores and overall performance increase is naturally due to 2 years of development, just as it always used to be, so we see smaller node, more VRAM etc. but it is still essentially a midrange chip.
So why would they keep chip development on the same-ish track but change the marketing names? There could be various reasons, introduction of future products in between, after they see how AMD's chips are doing etc. One obvious reason is also that newer smaller nodes cost significantly more than old 16-12nm, probably more than 75% more, so they get more performance but at a higher cost. And since the market didn't really like the large price hike with RTX2000, it seems logical to go with more performance=more money=higher ranking name, since the buyers' eventual discontent will be subdued significantly that way. And so the 3070 becomes 3080, and 3080 Ti becomes 3090..