According to the official twitter, mangaka Hata Kenjiro replied to a question from a Taiwanese fan about the third season of Hayate no Gotoku! anime.
@howdoeshe: HI!hatakenjiro I am your reader from Taiwan When will the third season come out?
@hatakenjiro: Thank you! The third season : after the movie of the summer of this year. Please wait in expectancy!
@hatakenjiro: Thank you! The third season : after the movie of the summer of this year. Please wait in expectancy!
Source: Hata’s tweet
