In the contract. Here's some other stuff. (Destiny)

by stabbim , Des Moines, IA, USA, Saturday, January 23, 2016, 06:37 (3322 days ago) @ narcogen

The initial tentative schedule was like this:

Destiny 1 Fall 2013
Destiny 2 Fall 2015
Destiny 3 Fall 2017
Destiny 4 Fall 2019

Since Destiny slipped a year, it would look like this:

Destiny 1 Fall 2014
Destiny 2 Fall 2016
Destiny 3 Fall 2018
Destiny 4 Fall 2020

So that's where people are getting their Fall 2016 expectation from.

Yup, and of course "Destiny 2" could slip as well. Probably that will happen less and less as Bungie gets better at planning Destiny development, but it's still possible. Also, Bungie decided to do away (or delay, I guess we don't really know) the DLC (and presumably Comet) for year two in favor of these smaller/more frequent "events," so the whole schedule is a big question mark at this point.

Nothing in it grants Bungie creative control of advertising and promotional materials.

Well, that explains a few things.