Really not a bad idea. The sequence does show humans or human forms engaged in a confrontation with one having some sort of telepathic pull/throw ability. Time travel is not out of the question either as it was used once before to market Halo 2 in 2004 via the ilovebees.com website.
Melissa was infected by a devastating Covenant program buried in a larger transmission. When the Deep-Space Artifact created a Slipspace explosion on return to Earth, she was blown apart, with some parts being transmitted to Earth of the present and others being thrown back in time to the Earth of the early 21st century.
So, could the slipspace jump (or malfuction) at the end of Halo 3 allowed Master Chief and Cortana to ,somehow, go back in time or forward in time??? Quite possible.....
Very interesting theory among many! Will have to keep this in mind.....