There's a man and a woman singing, so it's definitely not the original Frontin'. I clearly heard, "and I'm ready" at the end. It could've been a remix a I don't about, tho...
Ya there's no way that Beyonce is playing her new song out loud for her music video unless she's in the confines of a secure studio. Not after how secretive she's been. Not after someone was fired from her video shoot a few weeks back for taking video, not on crowded Coney Island.