Yes, it's true. There is a Tag Force 3, making it one huge Tag Force Trilogy. Heres the info straight from the website.
Duel Monsters GX Tag Force 3 Release: Autumn/Fall 2008
System: PlayStation Portable (PSP)
Genre: Card Battle
Promotional Cards: Unknown
- Uses the Official Card Game Master Rules.
- Features Season 4 Judai, Haou Judai, Yubel, Mr. T (Trueman), Johan (possibly Dark Johan?), etc...
- Seasonal events and the mail system make a return from the original Tag Force.
- The cards in the game go up to The Duelist Genesis, and may include any new Starter and Structure Decks that have been released up until June 2008 (SD15?).