So the Clash part was correct. However, it appears that Japan forgot an S somewhere in the Katakana.
— 【公式】遊戯王OCG (@YuGiOh_OCG_INFO) February 23, 2015
Yes, it says “Clash of Rebellions”
For those wondering, it says the set includes cards that make Raidraptor and Infernoids ridiculously strong. And new cards for the fan favorite “Red-Eyes” theme. And to please wait for further information.