Let me correct you there, SLI as we know it .. meaning SLI driver profiles is not getting less support BUT IS DEAD SINCE 1st Jan this year for all cards and 3000 series never got SLI profiles. Welcome to 2020's it is now NVlink and mGPU.
I have a 5120 x 1440p 49" 120Hz (basically 1 million pixels less than 4K) screen and dual 3090s , mostly for work but do game on it and have tried some of the games it supports with dual 3090s, eg. RDR2 at full ultra settings on will not hit a stable/locked 120 FPS for my 120Hz monitor but looks amazing. Try that on your 3080 Ultra settings all maxed out..
Shadow of the tomb raider fully maxed out is stunning too even with its not so great ray tracing features. I need to stick some results up on the benchmark threads and 3090 owners thread, when I finally have time.
I'm hoping MSF2020 finally gets the DX12 features and allows the use of more than one card. Then watch how many people jump onto multi card setups when MSF2020 gets the feature.