Considering the mad rush Kishi has been on to get us to this point after Pain's invasion I'm not so sure I believe that. The pacing for the past few years has been that of a guy trying to bum rush towards an ending, if he wanted to do a part 3 the perfect time would have been after Pain got beaten.
Rush?
It's been 4 years since the war started.
the calendar duration of the war spans practically the entirety of the Dragon Ball manga from start through the sparing of Piccolo Jr's life by Goku (or, in anime terms, the entirety of Dragon Ball)
Nov 20, 1984: Chapter 1 of Dragon Ball is released
Oct 10, 1988: Chapter 194 of Dragon Ball is released. (Chapter 195 timeskips 5 years later and begins the Saiyan Saga)
Duration: 1421 days (inclusve)
Nov 10, 2010: Gaara's Speech/Chapter 516 of Naruto is released
Aug 29, 2014: Today's date
Duration: 1389 days (inclusive)