My 2c on the graphics: from the (disappointingly little) we've seen of actual rendered footage, the port seems more about taking advantage of the PS4's to render The Last of Us generally as we know it with greater clarity and performance. Not online someone playing on a somewhat dated PC, doing an upgrade, and then being able to crank up the resolution, texture quality, filtering, etc. It is, in many ways, the same base game, but the increase in processing power allows for a natural increase in rendering resolution, the use of higher quality assets made during production, better filtering on shadows/aliasing etc, and of course improved average framerate.
It is a true "HD port" in the same way that a lot of lot of PS2->PS3 games were, and provides the best "experience" for the given assets and their made quality.
The difference between TLoU: Remastered and something like, say, Wind Waker HD or Halo 2: Anniversary is that the latter seem to involve more drastic overhauls of rendering systems and/or assets that more closely constitute a "remake" instead of a HD port. Wind Waker reused most assets from the GCN build, touched up textures, but completely overhauled the lighting/shadow engine (for better or worse) that on a technical level accomplishes stuff that was never in the original build (like ambient occlusions). Halo 2: Anniversary is a new engine and totally new assets, even if mechanically the base game plays the same way.
Some of this may be true for TLoU: Remastered and we just haven't seen it yet, but I tend to look at this port less like the above two examples and more like Resident Evil 4. Improvements have been made, some artistically others through nature evolution of technology, but it's not a true remake or asset/engine overhaul like some ports/remakes have. It's taking the base assets and rendering of The Last of Us and dialing all these qualities up to better suit the PS4 hardware. That is an improvement and will be a clear one when playing, and TLoU already looked outstanding on the PS3, but expecting a massive, full "next generation" graphical showpiece is perhaps a bit unrealistic.
