I went the other way -- from cello to bass. It shouldn't be too hard to make the switch. Just be careful that cellos are really small, and easily misplaced.
For a time during high school I played both cello and (electric) bass quite extensively, and the mental jump from 4ths to 5ths wasn't a big deal at all. In addition, much of what you are learning, in terms of bowing, musicianship, etc., are universal.