Can you run into other adventurers? Can they recruit you? On a possibly related note, can you conscript followers? Given our new-found vulnerability to numberless hordes, will world gen adventurers have companions or royal guards etc?
None of those have been mentioned specifically by Toady yet. A couple, such as conscription, have been implied as being part of Inn/Tavern development, but, as usual, no timeline.
Will we have abstract control over hill dwarf settlements layout? If we do get some kind of united expansive fortress, will we be able to change which part we directly control? Sounds similar to next door retirements and reclaims as you offered in the DF talk, theoretically.
Toady has stated that our interaction with sub-sites will be rather limited in this initial release. It will be less of abstract control, and more like indirect influence. By that I mean, we won't be able to order 40 barrels of whip wine a year and wait for the eventual delivery. But the population, strength, defensibility, wealth, etc. of our main fortress will/may influence factors that play rise and fall to components of our outlying linked sites. Also, Toady has said that in the medium to far-medium future, we will not be able to play as Hill Dwarf or Deep Dwarf sites, so directly controlling the floor plan of their sites is RIGHT OUT!