"Mission accomplished/successful"
"Mission failed"
There are times when you don't exactly know what happened while being the last survivor or spectating the wrong team mate and the game suddenly ends.
It's nothing big, we only have to wait few seconds to see the results, but I think it would be a cool gimmick if Betty could announce the outcome.
This would also be in line with previous MW titles. ("Nav Beta reached. Mission... successful!" - Oh how I loved how Betty pronounced "successful"

http://youtu.be/bonai7PXfUM?t=9m