I brought this up in another thread, but made the mistake of comparing the decision to Cannikon feature crippling, and my technical questions got lost in fanboy defense, unfortunately.
I've since found some interesting discussions on the Black Magic forums, where they talk about this same issue but with regards to 60p, instead of 422 10 bit. The basic issue seems to be the amount of data you are feeding _into_ the encoder, not the data rates coming out of it.
Some more looking around, and the issue seems to be with affordable encoder technology lagging the rest of the camera subsystems a little. As noted in this thread, the Odyssey 7 seems to be the only reasonably affordable device that can capture 1080p60, but it does it at 8 bit 422. Blackmagic and a bunch of other recorders do 10 bit 422, but only up to 1080p30. I guess there are must be some high end recorders that can do 10 bit 422 1080p60, but I suspect they must be running some pretty low production volume encoder chips (expensive) or using FPGAs for the encoding (even more expensive).
As such, given the current choice in the low budget segment seems to be high frame rate 420 8 bit, or max 30 fps 422 10 bit, I think Panasonic made the right call for differentiating their product. Certainly, as a rank amateur looking for a hybrid camera to take snowboarding and kiteboarding, the high fps appeals a lot more than 10 bit 422.