They look like power-ups you find or earn, not killstreaks.
I wouldnt mind at all if you could find them. That would be balanced and focus on map control. It would also probably be less frequent than what I imagine.
For comparison, Destiny and COD both have these kind of abilities, and when every character is popping them, they become quite frequent and annoying.
But it seems very clear that you select a character in UC4, who has a special ability/role. That's the vibe I got from the trailer, where the characters are all yelling out their catchphrase.
I just really dislike the trend of super powers in games. You just have this meter that fills up, and you bust it out when you want to constantly turn the battles. It just adds a random, chaotic element that often feels unfair or cheaply adds moments to a game to look special. I much prefer none of that, where the excitement comes from just your actions and positioning on the map.
I prefer the controlled, and careful gameplay of UC2, LoU, and classic Halo. I'm just not big on instantly spawning power ups or having A.I around.
A LOT of games are doing this today, and it's just strange to me. MP games heavily try to promote playing "Characters" now, who have their own abilities. It's a very MOBA-styled approach to MP.
I'm of course open to seeing gameplay, so the trailer just left me asking questions and feeling curious/anxious.