I'd say that in 10 years, Dwarf Fortress will have been completed. It will be a 2d ASCII game overlying a volumetric 3d world represented in blocks. Toady will have thought of everything you could realistically do in the world, and the difference between Fortress and Adventure modes will merely be whether you're playing The Hand Of God or a specific individual... but you'll be able to do the same things either way, and in certain circumstances jump between modes.
Start a Fortress, populate it, and hone it until it is self-sufficient. Then, once a Land Holder comes you'll have the option of turning the government of the fort over to them, "NPCifying" the fort and allowing you to select an individual Dwarf to become a Wanderer, Scout, or Beast Hunter as the case may be.
There will be many 3rd party utilities and interfaces that spring up once Toady has decided he is done with the game in full and releases as much of the API as he feels is necessary for people to continue modding the game. Mods at this time will be very extensive, and will range from simple tweaks to complete conversions of the game. The base game's simulationist tendencies will make it lend itself very easily to conversions of all kinds, from Fantasy to Post Apoc to Sci-Fi, anything so long as it takes place on the surface of one planet/world/dimension.
As far as the 3rd party interfaces go, there will be, after a number of years once active development of the engine ceases, Isometric frontends for Fortress Mode, and possibly first person conversions for adventuring. The First person modes will seem to be quite simple at first, due to the turn-based environment and block-based volumes. However, since development of them will be every bit as much a work of love that the making of the game itself was, they will be very functional, and probably play alot like the old Ultima Games... only with more depth.
So basically the game itself will take on more complexity and depth, but graphically will stay much the same, with the possible exception of showing more z-levels at once time and divorcing itself from the 16-color ANSI-like mode it's in. I'd like to say that it will become Truecolor Unicode TTF based, but that might just be a dream.