The official Japanese Pokémon Trading Card Game website has confirmed that
Wild Blaze (ワイルドブレイズ) is the next XY expansion and it will be released on March 15th, 2014. Players that purchase 20 booster packs from the set can receive a special promo
Numerugon card.
Mega Battle Deck 60 M Lizardon EX (メガバトルデッキ60 MリザードンEX) will also be released on March 15th, 2014. The deck features Mega Lizardon EX as the title suggests. Players that purchase the deck from March 15th, 2014 through May 18th, 2014 can receive a special Pokémon Card Game XY Promotion Card Pack (ポケモンカードゲームXY プロモーションカードパック).
Sources:
http://www.pokemon-card.com/campaign/xy2_box/