Or the opposite, that people will unknowingly transmit data over untrusted connections without this.
Your only option is to use a _different_ browser which trusts the old certificate.
You are right, but there's always a chance that the various documented HSTS bypasses might filter down to normal people. People might be willing to find and use them if they /really/ need access to the site.
e.g. Typing "thisisunsafe" in Chrome on the error screen, or flushing the HSTS state in the browser.