This news is right now everywhere on Twitter, the band has announce that they will play New York and London in November at the end of their Summer Sonic 2014 concert.
Carlor_Stonefist from Reddit on Twitter just tell us
I am at summer sonic, I can assure you, the babymetal New York and London concert rumors are 100% TRUE!!! They will be in November!
Babymetal just announced on stage at Summer Sonic that they'll play in New York and London in November.
— Daniel Robson (@NoMoreDaniels) August 16, 2014
Update 1: the proof 🙂
Update 2 : officlal