Although if I were upgrading, I'd consider 5600X/5800X only, truthfully, once supplies are semi-flowing...(you will survive with 'only' 90-110 fps until then, and without streaming, no Youtube , DVD-watching, and /or Discord while gaming, etc.)
You can compare CPUs below, albeit with 'only' a 2080Ti in the comparisons...
I just built a new PC... but not before my 3090 got a trial run for almost a month with my old 7700k system. 7700k is still a solid gaming CPU but I do more than just gaming and I wanted the additional cores/threads from the 10900k for video work such as encoding. Sure the 7700k was dated compared to the new GPU but it was by no means a massive bottleneck.
I actually loaded up MSFS2020 in max 4K ultra settings and the FPS is about the same with both processors... the difference is the 10900k is a lot smoother. My point being that it is an upgrade but don't expected an out of this world difference... like the poster above me said probably 25-30% at 1080p for that Ryzen chip.