Well, this announcement was obviously coming. Now that The Secret Life of Pets has fetched over $400M at the box office, Illumination has announced that a sequel is on the way, and it's already been set for July 13th 2018.
Original director Chris Renaud will return along with screenwriter Brian Lynch, both having worked on Despicable Me and Minions for the studio previously. So these two are a box office gold mine and it's no wonder Illumination is keeping them around. 'Pets' opened with $104M, the largest-ever debut for an original animated feature. It's the third animated film to be a box office juggernaut along with Zootopia and Finding Dory.
So far the voice cast, which included Kevin Hart, Jenny Slate, Albert Brooks, and many more, have yet to be confirmed but we can probably expect most or all of them to return.