There is an inconsistency in the way backwards-compatibility packages are named. Some (for example, compat-gcc and kde1-compat) have compat in their names and some just have a number. IMHO, it's much better to use compat since that would allow one to easily identify all the compat packages installed and remove them once they are longer needed. IMHO, it would be better if ncurses4 would be renamed into ncurses4-compat.
I agree that it's not very consistant, but renaming the package now after it has been called ncurses4 for the past 4 releases (and been a compat package all the time) would be even more confusing. (Besides, there's no real consistancy in the first place - look at e.g. readline41, libpng10 or the whole slew of gnome compat libraries (gal7 and friends).)