The 15th Pokémon Tretta set has been announced and it is also the 4th renaming updating for the game.
The Pokémon Tretta Ultimate Set 1: Dragon Ascent! Black Mega Rayquaza Soars Through (ポケモントレッタ アルティメット1弾 ガリョウテンセイ! 黒いメガレックウザ飛翔) features a
new class of Tretta: ULTIMATE.
Rayquaza, the first ever Ultimate Class Tretta will be introduced in this set and Serena's Panchan will
become readily available as a Master Tretta.
Pokémon Tretta Ultimate Trailer
Source:
http://pokemontretta.com/tretta/t15/index.html