These are from the newly announced map, Guardian (formerly known as Jub Jub). It’s a tree top map that’s the spiritual successor (read: Not remake) of Halo 2’s Lockout.
The videos are from the final Omegathon challenge at PAX (Penny Arcade Expo). The Omegathon is a tournament that runs during each PAX. One of the previous final challenges was Tetris.