Who lives from Halo 3?

Master Chief although in a cryo pod is still alive. But all you people with a sharp eye will notice that 117 (Master Chiefs number) is on the pelican wing that is a memorial.

Cortana Also because she wakes up John in halo 4 (Not out yet but coming out fall next year 2012 which roughly means 26 September for UK) in the E3 trailer.

Arbiter who returns to the Elite ship and takes command again after living the suicide mission that he is sent on in Halo 2, and living Halo 3.