Yes, I really waiting for this ! Run thunderbird on different PC and find back my config, tags, folders, adress book, add-on, signatures... It would ne great !
Full user sync is the only thing missing from Thunderbird for me. I use multiple computers, and find myself reinstalling my OS and apps frequently to test different Linux distros. Having the capability to sign in to my Thunderbird account to import all of my settings, and accounts would be a game changer. I could foresee this being a potential security issue, but assuming it can be done safely the benefits are obvious. Having this same functionality in Firefox is one of the major reasons I continue to use Firefox as my daily driver.