Can you comment on the feasibility of item/map graphics? As of July 2010, it sounded like Toady's main concern was the size of the texture atlas, but given how many creatures have been added since then (300+?), it doesn't seem crazy to add several hundred item/map tiles.
This is still a going concern, with the texture atlas working as it does now. I'd need to do some fairly hefty surgery to make it possible.
However, quite frankly it is not reasonable to maintain five separate renderers. The most likely path from here is to cut it down to three: One text-mode (curses) 'renderer', one SDL-based using only 2D graphics, and one OpenGL-based that will only attempt to work on up-to-date hardware that supports <significant parts of OpenGL 3> but will also support shaded/animated tilesets.
With a restriction like that, I'd be able to write clean code that avoids the limitations of the current OpenGL output, and with only two graphical renderers to maintain it'd be reasonable to support everything we want to support (TTF, etc.) on both of them.
Unfortunately the Intel drivers do not currently support OpenGL 3, at least on Linux, which means that implementing this would cut quite a few people out of the loop, notably including me. They
claimed they'd fix that by the end of 2011; they haven't yet.
EDIT: Eating my words. This was posted three days ago:
Mesa 8.0 is released. This is the first version of Mesa to support OpenGL 3.0 and GLSL 1.30 (with the i965 driver). See the release notes for more information about the release.