The official statements for Quantum Break's delay are as followed:

“With so many Xbox One games launching this year, movingQuantum Breakto 2016 extends our incredible portfolio into next year with a monster new IP,“saidShannon Loftis, Head of Publishing at Microsoft Studios.

“We’re really proud to be part of the incredible Xbox One line-up,“ saidSam Lake, Creative Director at Remedy. “We thank our fans for their patience, and want them to know that the team is taking advantage of this opportunity to polish and fine tune the game to create the kind of standout entertainment experience they've come to expect from us.“

We all must remember this quote so that delays won't upset us: