Well both my computers updated the browser today. So far so good.
The legacy section took out 3 of my addons, but luckily the other addons I've got, mainly adblock, ublock and internet download manager are working good.
The browser speed quickened up a lot.
I noticed in the options before I updated it, there is an option to not download the updates. So I wonder if you do that, then it just won't move on to the newest version? Though I guess you risk being compromised.
I also wonder about how Tor will deal with this, seen as they seem to use firefox as a base of their browser.