You're right , but that's a pretty difficult and expensive solution. The more practical solution for now is 2.5D stacking - stacking all the un-packaged chips

You're right , but that's a pretty difficult and expensive solution. The more practical solution for now is 2.5D stacking - stacking all the un-packaged chips on silicon/glass die instead of a pcb. That's already being used in some fpga and communications equipment. But 2.5d is still pretty expensive and complex. Not yet ready for low cost stuff.