We recently reported about the new PS4 model CUH-11xxA, and apparently there's also a revised DualShock 4 controller incoming, as made apparent by a new Federal Communications Commission certification published recently. According to the documentation provided, the revised controller will have the same code as the old ones (CUH-ZCT1U, the last letter varies as it indicates the region), while the FCC ID changes  from AK8CUHZCT1 to AK8CUHZCT1F1. You can see the new label below:

The use of the same model code mirrors what was done with the DualShock 3, which retained the same model code CECH-ZC2x (with just an addition for different colors) for the whole lifetime of the PS3, even if it went through several revisions.

Studying the documentation more in depth, we do see some interesting changes (you can see the spec sheet of the original model at the bottom of the post for the sake of comparison):

The changes in the data provided are the battery supply, which has been slightly reduced from 3.7V to 3.65V, indicating a possible change in the battery. Unfortunately this doesn't tell us what most would like to know, which is whether the battery capacity has been increased. It's worth mentioning that a 0.05V difference is not enough to fully confirm a battery change with absolute certainty, while it hints to it.

The antenna type has also been changed, from a PWB pattern antenna to an IFA antenna, which incidentally matches the new antenna introduced with the new model of the PS4. Differently from the battery supply, this is a definite confirmation of a change in the controller's internals.

There may be other variations in design, but since the FCC only certifies radio connectivity, they wouldn't appear in its documentation.

One thing is pretty much certain: Sony is definitely ramping up to sell a revision of the PS4, with a revised controller. The full extent of the changes is still a mystery, but maybe we'll hear more at E3.