I doubt any new types are being introduced. The last time we got new types it was simply to balance the game after the obsecenely overpowered Psychic typing in Gen 1. Nothing like that is even remotely in effect in Gen V.
The type chart is fine as it is. Some types are meant for offense and therefore have few defenses, others are meant for defense and have subpar offenses, etc...
The type chart is fine as it is. Some types are meant for offense and therefore have few defenses, others are meant for defense and have subpar offenses, etc...