Originally Posted by Kiwi Flyer

If you haven't visited any of the "problem" countries you'll be fine.

If you are affected by the new rule and have an existing ESTA authorisation at some stage US CBP will notify you (by email?) that the authorisation has been revoked and advise what you need to do (including special cases with imminent travel to USA).

At some stage the new rule will come into effect and at that point new ESTA applications will incorporate this.