I know this wont be that much valuable info when it comes to AAA, big budget, graphical showcases games but, I have a couple of indie dev friends, and one of them was notified ~4 months ago about NEO, since their game is coming to PS4 in a couple of months, and as it would be in the released in september/october area, it would need to have a ''NEO mode.''
They wont get a new devkit (at first at least), but Sony is releasing a new firmware for their current one. But this prob will only work for indie devs, which games dont require that much of the GPU power.
Also, Im sure this will be out in 2016, based on the wording Sony used on their briefing with them