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 pressed my Shenzen source for target selling price for 3090 but no news yet, however my local supplier hinted likely above 1k. Hmmmmm.....
No, prices would not be lower than the founders edition on almost anything. Not this year at-least.