Industry insider Ahsan Rasheed, also known on NeoGAF and Twitter as Thuway mentioned something he was told "down the grapevine" by his sources, explaining that Xbox One might end up remaining behind the PS4 for the whole generation:

Xbox One will be behind all generation, and not by some small trivial margin. It will be enough to show up distinctly in exclusives.

He continued by saying that while Microsoft's new console has some improvements incoming, the same will happen to its rival.

The PS4 has more left in the tank that will start showing up going forward. It was designed with more forward thinking hardware choices.

According to Rasheed, a Call of Duty: Ghosts coder also told him that Infinity Ward asked Microsoft to use an off-limits portion of the Xbox One GPU (allegedly amounting to 8% of the whole power of the graphical hardware of the console, and the the use of which should be granted to developers soon) but Microsoft refused.

He mentioned that developers are thankful for what many are now calling "resolution gate." as as it pushed Microsoft to unlock more resources, and while it won't bring parity between the hardware juice provided by the two consoles, every little bit helps.

As a funny side note, Rasheed mentioned that he received the following message on NeoGAF after revealing the details quoted above: "Don't you dare get people's hopes up. Xbox One will always be behind and the gap will widen." The identity of the sender hasn't been revealed.

As usual, with everything that comes from insiders like Rasheed, we should take this with a grain of salt and consider it just a rumor. That said, he demonstrated many times to have solid industry contacts, and his predictions normally match up well with what actually happens.

We'll have to stand by and see if the prophecy will come true in the next few years, since the "next gen" has just begun. Saying that the Xbox One will be behind for the whole generation might definitely be premature.