A photo confirming Monster Hunter Portable 3rd as a PSP game leaked onto Twitpic and Gigazine grabbed it before someone pulled it. Look for more news about it soon, perhaps later today.
Update: Capcom sent out a press release confirming the news and an international name, Monster Hunter Freedom 3. This version introduces new regions, monsters, and a revised Felyne combat system. Look for Monster Hunter Freedom 3 in the Japan in late 2010.