A custom chipset does not have to be built by the same company who designs the computer. For example the X-Box uses a nVidia chip or the Game Cube an ATI.
But what's exciting with this is that the hardware is fixed and it's powerfull hardware. Moreover on the X-Box you get shared memory which allows so many optimization tricks (just benchmark a main memory to video memory copy on PC and cry as it is so slooow).
When a company sells a game for a console, they do not label on the package with stuff like "this game needs this or that hardware". They just label it "X-Box game" or "Game Cube game". No wrong hardware, no wrong driver... You put it in your box, and it works.
That was really a nice thing with the Amiga. You just had to put "Amiga software" on the package and you were about 100% sure it would work on your Amiga.
I've been programming many years now on PC, and I don't count the times I had to correct "compatibility" problems in my softwares, or deal with users why the software could have troubles on their PC :
"Oh yes, for running this software featuring high quality real time 3D you NEED a 3D card"
"No, it won't work with your old 2 Mb 3D card"
"Oh, well, I code with an nVidia card, I don't really support ATI cards but it will work, it's just the program won't be as fast as on an nVidia one"
"Your sound card doesn't support hardware channel mixing so you will have to install DirectSound on your computer to make it work"
"Oh, well, it seems that the high resolution timer interface on your PC is not working properly. It might be a problem with your motherboard. First time I see this..."
...
I'm afraid it will be the same with the new Amiga. One of the great advantage of the old Amigas : "the plug and use concept" will be lost. With consoles if a piece of software works on the developer platform, let's say a Game Cube, it will work on ALL other Game Cube of the world. Something quite impossible on PC. Something lost for the Amiga :-(