A new trademark registered by Sega for a game titled “Valkyria Duel” has appeared on the trademark database in Japan. I think it’s safe to assume that this is something related to the Valkyria Chronicles series but what it is exactly is currently unknown.
My uneducated guess however is that it’s some sort of bundle release, possibly of Valkyria Chronicles 2 & 3 for the PSP. Sega has released other “duel packs” for PSP in the past so that could very well be the case. Regardless, I won’t get too excited until I hear the unlikely announcement that it’s coming to the West.