Well it does say "until at least fall 2016" so that means no earlier than fall 2016. And it still is not going to be earlier than fall 2016. So there is no lie there
Now if they said "by fall 2016" that'd be different.
The theory I believe, is that the contract with Sony was that the exclusive content was contract from the taken king until the release of destiny 2. And since destiny 2 go pushed back to fall 2017, that exclusive contract got pushed back as well.