It'll recognize when succession is necessary and try to schedule things effectively, and I set up a claim system so that there can theoretically be more than one person that says that they hold a given civilization's position (three dwarven counts vying for an open monarch position, for example). Competing claims don't have a resolution yet, and I need to work out appointment lists properly.
From this it would seem the the claim system is not complete, so resolution of several claimings is not determined just yet. I guess it could be at random (I would start with that at first if I where programing the game), but maybe we will end up with some fancy mechanic to determinate it, like competitions, assassination attempts (great quests for an adventurer I guess) and even civil war?
You seem to be assuming/jumping the gun a bit here, that ToadyOne is done with the Succession system. He probably just giving us a normal dev post, of where he is, and whats been done.
Will any of the position succession stuff that you are working on allow for things like the assigning an office to the position (such as mayor) instead of an individual dwarf?
The succession stuff ToadyOne is talking about, is the world progression during play. While this will have some affects for fort mode, he hasnt made any indication that this (room designation) was changed, or that room designation in general are being reworked. I would also hammer a guess that room designation and world progression during play, are not related to each other.