Hello Bélà,
moving ncurses out of base sounds like a good idea. The only program in the base that depends on ncurses is /usr/bin/tset, which itself is not executed from any other program of the base. Once the decision has been made, on what to with it (remove or replace), there's only one thing left to do before ncurses can be moved out: write a script that peeks into the extensions if they link against ncurses, and add a line to a .dep file, if they do so. Both requirements can be taken care of on a rather short timeframe, probably even during the current rc phase of 3.1.
Greetings,
SvOlli