The word on the Internet is that the third bus loop at the Magic Kingdom will open Sunday, November 24 (tomorrow, as I post this).
The word is also that the additional bus stops will allow Magic Kingdom bus service to and from Disney's Hollywood Studios and Disney's Animal Kingdom, which previously operated from the TTC.
The additional curb space sets the stage to allow larger, higher-capacity buses, although this might require reworking some of the existing bus stops.
As far as know, none of this has been announced officially, as of today. But if various bloggers are correct, we'll know tomorrow.