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.
I'm not sware of any new instructions except FP64 which is of no use in mining so I'm not expecting any signficant coding improvements,
even for compute bound algos.
The new compiler and runtime might provide some minor improvements but unlikely to be significant.
The default intensity will need to be updated for the new cards but it can always be set manually.