I can't imagine re-releasing REmake and RE0 in HD because they'd have to re-render everything. I doubt those backgrounds were done in very high res; they even look murky on the progressive scan Wii releases with component video.
RE4 in HD would be marvelous. They better get it right and make it the ultimate version of the game this time. :p I was pissed when I got my HDTV that I learned the GameCube version isn't anamorphic widescreen. Then I was pissed again to pick up the Wii copy and discover that, despite automatically filling the TV, it's not true widescreen—it's just the GameCube image zoomed in with all the same amount of pixels, and zooming in on the GameCube version looks exactly the same, so the resolution's probably more like 300-something by 640 and I think the video's interlaced to boot. THEN I was even MORE pissed to learn that the PS2 version, despite its lack of certain graphical effects, is true 480p 16:9 widescreen and looks much better for HDTVs. :p Fuuuuuuck!
So, a 720p 16:9 upgrade would be fantastic, and it had better feature everything that's in the previous versions.