This reporter believes the new PoV is that was not revealed is in fact Brienne. GRRM first reported that he struggled with the idea that there was a five year gap but that important events occured within that time period. So, he decided to scrap the five year gap and push A Dance with Dragons to be the fifth book. The Winds of Winter will be the sixth book. Parris is betting that the series will extend to a seventh book but Martin still wants to keep it to six.
But, I digress, the main reason he struggled with the gap was that important events could not be related via flashback BUT would have to be if there was a gap. In fact, he said that the unrevealed PoV was the main reason for this. This makes me believe that the new PoV is Brienne because she had taken Oathkeeper and was actively searching for Sansa. Also, I have repeated asked him for a Brienne PoV and when he announced that there was a PoV that he was not going to reveal - he looked my way.