I am really happy to see this and I would be absolutely ecstatic to see this announced at PSX. I would be thrilled if Sony had a system akin to Microsoft's system where I could put a disk from my very sizable PS2 collection into the PS4 and it would register that I own the game, so I could download it for free.
The higher internal resolution, post-processing, and higher frame rate are super nice improvements. While PCSX2 does exist, it requires a reasonably beefy computer to run all PS2 games well -- and even then, it's a case by case basis whether or not the game actually works (I was super disappointed when I tried to play Up Your Arsenal with my friend with PCSX2 and the textures were basically non-existent).
The Emotion engine is complicated, so I figure Sony has some upper hand when it comes to emulating it.