What I think is really interesting in this is not the possibility to use 16 millions colors per se, but rather the ability to directly specify the RGB components of the color to use.
The current approach used by terminfo and ncurses is to refer to an index within a palette, which has the drawback of giving little guarantees about the final shade of the color. (Look at the color table here [1] for a comparison among different terminals; here it is stated that xterm changed the RGB components of two shades of blue from one version to another!)
Allowing true colors in terminals would make curses programming very similar to what you do in HTML and CSS, where you directly specify the color you want. It would surely be a nice improvement.