They could just be higher resolution renders for print/web. The background textures seem to be intended for a much lower resolution.
Anyhow, I'm happy that the main series will continue and they'll also be working on other series as well. Although the term "milking" gets thrown around a lot here, they haven't made a bad Yakuza yet, and IMO each one has improved upon the previous one in huge ways. It's not milking... it's more like "strike while the iron is hot."