Update: Sorry, this was announced in the press conference last night. We missed it. The UMD is National Treasure 2.
According to this Kotaku story, Sony's announced a new $200 PSP bundle for the American market.
The pack will include a silver PSP, Ratchet & Clank Size Matters, a UMD movie (title TBC), a voucher to download Echochrome and a 1Gb memory stick.
October release, apparently.