It has been mentioned that some buildings will be locked, and other you will be able to build BUT the benefits will be locked.
Quote from the Dev journal.
As you continue to grow your land, build new structures, and expand the community size it will follow a similar pattern. Here are the actual requirements:
Hamlet: 3 Parcels; 10 people; Well
Village: 9 Parcels; 25 people; Tavern
Town: 25 parcels; 75 people; Town Hall
City: 49 parcels; 150 people; Courthouse
Capital: 81 parcels; 250 people; Monument