I actually anticipate that this generation will teach all of the companies the lessons that "Graphics do not sell consoles" and "Price Matters" ... I don't expect to see any console in the next generation sell for more than $300 (US) unless we see mass inflation.
From a hardware perspective I expect all three manufacturers to move towards a lower cost system based off of an asymetric multi-core processor that is designed specifically for gaming. AMD/ATI have been working towards integrating a GPU onto the CPU to produce a low cost, low energy, moderate performance solution for home computers; hypothetically speaking they could probably release a dual core processor today that had one or two CPU cores from a X2 and the GPU core from an X800/X1800. By the time the next generation begins you should be able to produce a CPU, Physics Processor, Audio Processor, GPU and a large cache of onprocessor memory as one large or two smaller processors (depending on whether you're using a 45nm or ~32nm process); it would also include a large supply of off chip memory.
As far as media goes, I expect most of the manufacturers to move towards a HD-optical media and have a pretty robust download service.
As far as controllers go I expect all of the manufacturers to incorporate some elements from the Wiimote (probably asymetric multi-part controllers that have motion control) with each company adding their own elements to it. One may end up producing different attachments than the others (a 4 button nunchuck rather than an analogue stick nunchuck as an example, or a touch screen or whatever) and the wiimote will undergo massive changes depending on the manufacture (more buttons, variety of layouts, etc.) but will be there in some form.
