Tor Browser auto updates so all users should be on the latest version. Tor Browser updates are normally accompanied by at least one security fix, so no one should ever be running old versions of Tor Browser.
However since the current stable Tor Browser only ships with Tor 0.3.1.x and >=0.3.2.x (the current alpha series) is required to use v3 onion services, no one except those using the Tor Browser alpha series (currently 7.5a9) will be able to access v3 onions.
I wouldn't migrate until the stable Tor Browser release is shipping a version of Tor >=0.3.2.x. There is no reason that you cannot run both services at the same time though.