I did some tests on the PTR, and I can confirm that
Predatory Strikes does
not affect the AP that got converted from str when they changed feral weapons. Therefore the conversion is in fact a nerf for us, since we can't benefit from SotF or Kings for that AP. I'm guessing that blizz won't change this, since the talent was obviously intended to only affect FAP since feral weapons always had str instead of AP in the past.
The weapon I used to test this is
[Origin of Nightmares], which gives 2085 FAP and 154 AP. In cat form, equipping OoN increases my AP by 3039 on the PTR. Considering the 100 agi it has, I had to reverse engineer the total AP formula, and came up with this:
(2085 FAP)*1.2*1.1 + 100agi*1.1*1.06 + 154AP*1.1 = 3038.2 AP
The FAP gets multiplied by 1.2 from PI and 1.1 from HotW, the agi gets multiplied by 1.06 from SotF and 1.1 by HotW, and the AP only gets multiplied by 1.1 from HotW.