The two-part Team Rocket vs Team Plasma episode has been pulled from the schedule out of respect for those affected by the earthquake and tsunami.
TV Tokyo had pulled the airing of both episodes from their schedule and instead are going to air Ash’s battle against Castelia City Gym Leader Arti. This episode was originally set to air after the two-part event. TV Tokyo had commented that they will show the Team Rocket vs Team Plasma episodes at a later date.
The last time an episode was pulled from airing was back during the Advance Generation saga. Episode 375: Shaking Island Battle! Barboach VS Whiscash! featured a whiscash that was causing earthquakes on an island close to Mossdeep City. Prior to the airing of the episode was an earthquake that had hit Northern Japan. Out of respect of those people affected by the earthquake the episode was pulled and delayed from airing.
To this day they haven’t shown the episode within Japan nor any other part of the world. The Rocket vs Plasma episodes could receive similar treatment since a trailer had shown Castelia City under attack (such as scenes showing windows shattering.)
The difference between the Advance episode and the episodes in question is that the Rocket vs Plasma episode could be considered as important plot points in the Black & White/Best Wishes storyline. This episode will be the first time Team Plasma has been featured in the anime.