miner software optimization might get 3090 to 150mhs...hopefully 
No, Eth is memory bound, 3080 and 3090 have the same memory type and speed so the minor difference we will see would be due to 320 vs 384bit bus width. And this isnt on-die HBM, dont expect 90+ on anything.
1080 is 35mhs
1080ti is 50mhs
that's 42.8% difference between 1080 and 1080ti, both gddr5x
Umm ... the 1080 was a GP 104 with 256bit bus width. The 1080ti was a GP102 with 352 bit bus width, thats where the hash increase is coming from. That, and better binned memory that can clock higher.
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3080 is 100mhs (there is a post that says 115mhs at 300w) if you do the math of adding 42% of 3080 to 100mhs that's 142mhs.
now nvidia says 3090 as titan like(they phased out titan, this is the new titan), if 3080ti is not released yet, then 3090 is better than 3080ti
if 3090 is better than 3080ti, then 150mhs is not impossible.
I dont think you understand anything about hardware, hash-rate or how the two correlate. I recommend some more reading.