Oh, what could it be? Probably Valkyria Chronicles 3, especially since Valkyria2.jp links to Valkyria Chronicles 2’s website. While this is no confirmation, it definitely shows that SEGA is, at the very least, interested in doing a third title.
The real question here is, what platform it will appear on. The franchise switched from the PlayStation 3 to the PlayStation Portable with its second entry, although that move didn’t seem to be well accepted by a lot of fans. Despite this, it seems the title still performed fairly well in Japan.
We will have to see how well Valkyria Chronicles 2 performs in the Western regions when the title launches on August 31st in North America and September 3rd in Europe.