Wish it was a little easier than just using the never version. sigh.
What's up with using a "never" version?
From the sound of it, it won't work well either way.
Updating a KiCad project to the new version should be easy and flawless.
KiCad V5 is quite old though. A problem with KiCad V5 is that it uses direct links to symbols and footprints from the project to the libraries, and it "caches" these in separate files too for "emergencies".
Unfortunately, quite a lot of people either delete or fail to backup these [project]-cache libraries. They also seem redundant, because KiCad V5 "fixes" these files if they are missing from the original libraries. But when you migrate a project without either these cache files or the original libraries,then KiCad can not find any graphics for the schematic symbols and it shows the dreaded [??] symbols in the schematic. The cache libraries in the project directory are important, and should always be kept and backed up with the project itself.
But all this is mostly a problem of the pas for most people. From KiCad V6 onward, copies of all schematic symbols and PCB footprints are saved withing the schematic and pcb files themselves.