You’ll be notified of new features while they are still in a state where you can try it out early (opt-in) and turn it off temporarily to fix any issues caused by the change (opt-out). If a change is going to become permanent (which means you can’t opt-out) and you’ve currently turned it off, we’ll let you know.
This section describes that in a little more detail:
Right now, you’re seeing only experimental changes because we migrated those over from the settings area to Upcoming Changes, but in the future there will be non-experimental updates here, too. So “labs” doesn’t feel accurate for how we are using this system.