On January 24-26 at the London toy fair they will be showcasing a brand new warthog. This info is courtesy of Halo4Follower and the link to his vid is here youtube.com/index?desktop_uri=%2F&gl=CA#/watch?feature=m-feedu&v=-hjd7UKLzi8
And here's the link where he got the info from www.ibtimes.com/articles/282149/20120116/halo-4-characters-vehicles-revealed-jan-24.htm