I guess I just don't understand why so many people thought Valkyria 3 would be on PS3. I can't think of any precedent for this kind of move.
It's true that Mario, Kingdom Hearts, Metal Gear and Shin Megami Tensei have all had mainline games on portables and will presumably have future console iterations ahead. But that's not this situation.
As soon as Sega added that 2 to Valkyria Chronicles for PSP, I think they were acknowledging that the PS3 would never be receiving any further sequels. In this case, people were asking for a sequel to appear again on the same original console after a handheld version, and that seems to be a situation without any precedent at all.