You all realize of course that if they do change the rules, it won't be retro-active - currently certified aircraft would be unaffected. Even aircraft currently in development (e.g. 777X) would be unaffected because the cert basis is effectively frozen when the airframer makes the initial application (there is a five year limit - which can become a can of worms when there is a big delay such as happened on the 787).
In short, the first aircraft to be affected by any changes to the passenger evacuation standards hasn't been launched yet.