Well, they just have to avoid releasing the same week as a major title in March 2016. It doesn't help that Street Fighter V is also planned to release sometime in March 2016. Just avoid releasing on the same week as a major title so you can maximize marketing resources and aggregate the most attention for your game.
As far as the delay, this is one I fully support and expected. Why would Square-Enix release Just Cause 3 on December 1st then next week release Hitman? Give your major titles some breathing room between each other.
On another note, 2 December 2015 games have been delayed to next year. Just Cause 3 and Xenoblade Chronicles X are the only major titles in Dec 2015 still standing, and something tells me both won't be delayed to next year.
