I have to disagree with selling off the EF lenses. I've been shooting with Canon for 40-years and went through the transitions of FD to EF lenses. This is like then. With new EF lenses there was no backward compatibility. Sure there were FD to EF adapter, but they sucked. The only way forward was with the new mount.
Today, while the RF lenses are excellent (and eventually I will transition some of my lenses), there isn't the absolute need to abandon your EF lenses. Will they lose value. Sure. But so do your cameras et al -- and those lose value more rapidly. I can't tell you the number of orphan accessories I have (such as the wifi adapter for the original 1D and 1Ds, or the wifi adapter for my old 1Dx).
Only sell if you have a real need at this moment. Haring, you never really said what lenses you own that you want to sell. That is the big caveat to all of this. If you have the original EF 24-70/2.8L, run, don't walk to unload it. If you have the 70/200/2.8 L II, that is still a keeper.