It's confirmed now: IGN: E3 2008: PSP Sizzle Reel Titles

Quote Originally Posted by IGN
NOTE: The PlayStation 3 game Valkyria Chronicles was shown at the event as a PSP title, but this was a mistake by Sony -- SEGA confirmed that this footage is from the PS3 game and there are no plans currently to announce a PlayStation Portable version of this game
Thanks a lot, Sony >_<