(Will DF get a framerate boost from PhysX cards at that point? )
I know you're joking, but it has been a serious request, which brings up the question: How does a PhysX card help a sprite game?
People have put in actual requests/suggestions to accelerate the physics in this game with hardware support? Wow. My best guess is they aren't programmers themselves and don't know what the PhysX cards actually do. AFAIK they basically just take a handful of vectors and do matrix math on them very fast, offloading it from the CPU. (caveat: I have not investigated this personally, but I have programmed a 3d engine with a friend and this is my best guess as to what they would be accelerating, based on the reported results of using one in a game which is written to support it)
The effort involved in coding support for them hardly seems like it would be worth the TINY tiny bit of help it might be to a game like this. And I do mean "tiny", and I do mean "might" - there are no particle effects in here that don't fill an entire tile, and not really a way to make such things meaningful, so the amount of help it could be with smoke drift direction and such is really miniscule. MAYBE their API has built-in functions for calculating fluid effects (pressure, flow, and such) but again such things are not worth accelerating at all on a tile-sized scale, and a sub-tile scale is virtually or actually meaningless.
So yeah. To actually write PhysX support for this game would be a negative result on time invested. IOW, the amount of time spent doing that (compared to making other, actually useful code) would be worth more than the amount of CPU time saved on the computers of every Dwarf Fortress player in existence.