I still plan to get a 5090 the math a bit different for me since am coming from a 3090. I would be getting a 250% increase over 3090 base on same math so that pretty huge and worth the price for me personally.
Can always play the next one will be a big increase game and maybe that true or maybe 6090 will just be another ~30%, I rather just stick with my every other gen and not try to play guessing games on which gen will be the good ones.