I believe once vaccines and better treatment are generally available and proven effective, it will be a cue to very quickly abandon excess caution for most people, even those who have gone to the extreme.

Larger countries (including the US) that are more sparsely populated and tend to rely on central messaging from authorities less will probably have areas that are slower at adopting new measures (or lack thereof), which may be frustrating, but I imagine large cities will be able to react promptly.