I just read a post on the IW forums which says that the kill streaks carry over;

Example: You get 2 kills and a UAV in the first round, and your team wins (You have 2 kills, 0 deaths)
The next round you get a few kills but you don't get UAV again, it ADDS the previous rounds kills to your score, so you get a heli or whatever!

I guess they're doing this because of the such low player numbers in a map Vs the sheer number of Streak rewards.

On PC before you COULD have 20V20 in SnD, and there was a chance you could get to an 11 kill streak, but now with matches that are going to be 3v3 or 6v6, there would be no way other than TDM to get those higher achievements.

Lame.

(Also, just a side note; does anyone know how One man army works REALLY yet? So far i believe that you can switch classes mid-game without dying, it takes 5 seconds (3 with pro) and you can only switch to a class with has OMA in it too....so couldn't you just set ALL 5 custom classes with OMA and a launcher, and then get 10 tubes PLUS 10 frags in a single round? or can you only use OMA once per round?....noob fest indeed)