The issue is how much is in the docking station, and how much is baked into the device.
This is not a terribly new idea. Many "Old" (like REALLY REALLY old) docking stations for first generation laptops had actual ISA slots and stuff inside them, so that more powerful desktop grade hardware could be inside the docking station, cut down on weight and thickness of the device, as well as cutting down on power draw.
short trip down memory lane on docking hardwareWith a phone, you are limited more and more by what you can reasonably drive for 4 to 6 hours on a 3500mAh LiPO battery. Granted, ARM processors sip on the juice rather than gorging themselves like a gourmand, but the power draw is still a significant design consideration for these devices and the hardware they have inside them, along with total size and weight.
When you start trying to make these devices also be beefy enough to do desktop oriented tasks (which is the whole point of a dock like this), then you start throwing a vastly different set of needs around, and the underpowered hardware of the phone is going to be a problem.
Now, it is possible that a great deal of fancy hardware could live inside the dock, attached by a lightning port or something. (Lightning has a high bandwidth and supports DMA, which means you could put lots of useful things on it, like a GPU, a hard disk controller, etc, and not bog down the CPU.) If they expose actual bus pins to the dock, the dock could contain an additional processor, and RAM as well.
I guess what I am saying is that rather than something completely new, I am having an intense feeling of deja-vu. First generation laptops were so underpowered it was hilarious. Compared to an actual desktop system that you can get for about 300$, your cellphone looks like a computer from 20 years ago, just very small.
It will be interesting to see where this goes, but I see it as being a novelty, not a new paradigm, and see it as just a modern evolution of an old idea.