I noticed that since the new firmware was released and many people started to complain that Phantom 4 Pro is unusalbe (https://forum.dji.com/thread-103711-1-1.html) various second-hand web sites got flooded here with second hand Phantom 4 Pros. Would it be wise to buy such AC now and wait for the resolution of the issue? Or do you think it will take ages till Phanotm 4 Pro will return to its past glory, if ever? The firmware is not downgradable as far as I understand.

Wait if I were you

Wait for better price......there will be thousands for sale shortly. Folks unloading paper weights.