Allegiant to be split into two films

Following the standard for franchises these says, the Divergent trilogy has made the double-finale move and will be splitting Allegiance into two films. As far as Divergent goes, we will see the second installment titled Insurgent on March 20, 2015. The two-part finale will begin on March 18, 2016 and will end on March 24, 2017.

The standard began with Harry Potter and the Deathly Hollows. Since then we have seen a double finale for The Twilight Saga with Breaking Dawn parts 1 and 2 and will get the first part of The Hunger Games finale, Mockingjay, this November. 
Divergent has had a decent start after making $117 million domestically in its first three weeks while Veronica Roth's original trilogy has sold over 20 million copies. Box sets and ebooks have risen in sales as well.