From my understanding, after the shattering happens and we log in for the first time, we will see a cinematic. This is to show us (the player) what happened on an individual level rather than trying to have a massive server wide event that you either only see if you are online at the right time, or if it repeats every hour (both of which would be really annoying).
My question is, will this be a new cinematic that we've never seen with the zones being destroyed, or will it just show us the "Deathwing is angry" cinematic that we've all seen before?