We all hope/pray that Toady can/will someday refactor for mutlithreading
Not all of us. Dwarf fortress is almost certainly in the state where it's mostly hard to parallelize and comparatively easy to improve sequential performance.
Double that.
I did some research on multi-threading, and it turns out a multi-threaded program is actually multiple programs working on the same data set. This is not easy, and many experienced programmers don't even try.
Moreover the stuff that sucks your processor power in DF is not really easy to separate from the main game. Pathfinding and fluid dynamics can be completely changed by a single wall, which means you need code to make sure those things always know where your walls are planned and instantly know when they're built. I could easily imagine a situation where those things get their own thread, but the game slows down because the main thread is always pausing to shuttle data between the subthreads, and then pausing to make sure that the data is still good...
Toady could probably take some stuff out of the main thread without problems. For example those meetings with diplomats, calculating whether you get sieged this month, but multi-threading that stuff won't speed up the game much.
OTOH he's got a few ideas to help pathfinding without multi-threading.