He has also said that he would like to write about the next generation, Naruto as a father because he is a father now. It has also been published that there will be a big announcement in 2015 regarding the manga. It has also been shown in the scans recently that there is a short spin off.
Bottom line, there are lots of hints to support whatever theory you have. My personal theory is that you have to follow the money. Shueisha is not giving up the huge amounts of cash that Naruto generates. Kishimoto is the author, but author's work for publishing companies. Shueisha only has to provide the proper pressure/incentive to get Kishimoto to write a part 3. For example, the announcement about the The Last was released as the "opening" of the New Era project. Look at how much attention it is already getting. People are going wild about the kids of the characters. I suspect the box office sales will be huge. That is going to be more incentive and more pressure to keep the series going.
So stay tuned. Part 3 is not a wild bet.
