We have arrived.
Well, this has been going on, or at least people have been trying to make it work, for some time. This is a major annoucenment of a large mobile (traditionally voice) provider essentially giving the green light to let go of the voice business and focus on the data pipe.
It is now a massive flat rate, on-net game. A race to the data bottom. The mobile "phone" will die and the mobile data device will thrive. O2 will pressure T Mobile to lose the silly surcharge for VoIP. Others will follow. They will have no choice but to compete.