Watched the trailer again...

In the fight against the big YoRHa robot at around 1:44, there's been a lot of talk about the screens on the back displaying the YoRHa motto, "For the glory of mankind". I think what's more relevant is what's on the big screen below that - we have R030 and a countdown, which in the video is at 6. In NieR, R030 is a Pod Program, one of the special secondary attacks 2B can use with her little robot buddy. R030 is Hammer, specifically. There's also stuff like R010: Laser, A060: Physical Shield, R040: Blade, and A130: Bomb. Seventeen in all.

That has to be a mechanic indicator, right? The boss will perform a mechanic based on the associated Pod Program when the countdown hits zero.