Platinum Games’ freshly-announced Vanquish has not yet been officially announced for any system, nor has a publisher been revealed. However, anybody with a brain could work out that there will be a PS3 version, and Platinum will continue its relationship with Sega.
Do you remember that leaked Sega document from last year? The one that promised Dreamcast games on the PS3 and various other sordid details. Vanquish was mentioned on it, long before we knew what the game even was. The document mentions that Vanquish provides an “opportunity for PS3/PSP interoperability.”
You can take that to mean that Vanquish may use both the PS3 and PSP to enhance the overall game, but until we know more gameplay details, that’s mere speculation. In any case, Platinum Games owns my soul, so Vanquish will be one of my most closely followed games. Once we know more, you’ll know more.