According to Variety, Pixar’s Up, scheduled for a 2009 release, will follow the adventures of a 70-year-old man who teams up with a wilderness ranger to fight beasts and villains. Pixar veteran Bob Peterson is writing the script and will co-direct with Monsters Inc director Pete Docter. The site also reveals what seems to be the first piece of concept art for the film.
Story info on Pixar's Up