I'm hoping for land selection sometime in June. (No basis for that.)
If i'm not mistaken there has been no mention of time-frames of land selection since the late spring comment that was made not to long ago, so id assume that's still the goal time period. I do think that we will get to see a basic shape of the land/continent, however i have no idea about what their plans are for locking biomes and or resources.
SBS is currently working on continent generation, which includes the placement of biomes. Once continent generation is complete, land selection will happen. I assume that players will get some kind of general overview of the location, climate, and resources available in each land, but I don't know what format that information will be released in.
Just to make it clear, land selection will happen only on Exposition. Now we will have server and settlement selection, in order of your title (baron/mayor+). June is a good guess thought. If you are Gentry, you will need to wait until Exposition to choose your lands.