Have a look at this video of the war games, and take a look at 0:32, just before he goes for the assassination he propels foreword with what appears to be rocket boots, which leave a smoke trail. Could this be another AA, possibly a boost AA, lemme know what you think 
EDIT
Also something similar at 1:06 of this video
I believe that’s the Jetpack. I read a description of it somewhere and that gameplay matches the description
There are two AAs that boost. the first is the Jet Pack which boosts you up, the second is a thruster that boots you forward. Its shown twice in the new videos. We know they are different because the Jet Pack looks different and only shoots the propulsion downward, while the other one looks different and shots directly out the back.
it’s called the Thruster Pack and it’s the replacement of both Evade and Jetpack
… I’m pretty sure. may be wrong, but highly doubt it.
Yeah, it’s the thruster pack. The sparks are probably from the blast getting diverted so the spartan can move laterally.
Ah ok cool, cant wait to see how this will affect gameplay