So with the Yakuza Isshin demo on PS4, we get first playable glimpse at how Japanese cross-gen looks/feels. Basically, outside the cutscenes (which look really identical since they're 30fps and the cutscenes were usually pre-rendered in the PS3 games anyhow), the game looks and feels really nice at 1080p/60fps. It has a sharp crisp look and feels super smooth without ever dropping a frame. If they start using some AA (jaggies aren't bad, especially compared to sub-720p PS3 Yakuza games; pretty minor but still there) it'd look like how I always wanted PS3 Japanese games to look.
So yeah, it's basically PS3 emulator'd edition; Japanese PS3 quality gaming without the IQ defects and better framerate. It's not enough to really convince anyone who wasn't getting a game to jump and get it on PS4, but if it's a PS3 game you'd want to get anyhow, it's definitely a nice improvement.
Right now there's just Yakuza Isshin, Dynasty Warriors 8XL and Guilty Gear X3rd announced for cross-gens. Fingers crossed that Tales of Zestria gets a PS4 port along with the eventual Gundam v Gundam Extreme Versus Maxi Boost. P5 is probably a lost cause since Atlus is too small and can just re-release it on PS4 a year later at full price with some additions as a director's cut.