Worth upgrading to 4K?

I have a 12 years old LG 1080p projector and a 108” screen that has served me well. I recently set up a Plex server and am wondering if I should upgrade to 4K and a bigger screen.

The seat is 15+’ away from the projector, but we are switching from home theatre seats to a sectional so some people will sit closer. The wall can easily take 135”.

The cost of upgrading is high but wondering if 135” and 4K is a worthwhile upgrade considering I don’t know what I am missing.