Eurogamer reports that a (since deleted) LinkedIn profile of AMD's senior manager of SOC (system on chip) physical design showed that he "successfully planned and executed the first APU for Microsoft's Xbox One Game Console in 28nm technology and a cost-reduced derivative in 20nm technology."
Reducing the APU of the Xbox One from 28nm to 20nm means that AMD can reduce the manufacturing costs of the processor because more of those chips will be able to fit onto the silicon wafers used for production. It can also lead to a chip that needs less cooling to operate due to the processor operating without as much power. Microsoft could use all of these changes to launch an Xbox One with the same hardware requirements as the current version but in a much smaller case that could be sold at a reduced cost.
There's no word on when, or even if, Microsoft would released a "slim" Xbox One but it has launched two smaller versions of the Xbox 360 since the original one was released in 2005. It would certainly make sense for the company to make a smaller Xbox One if it had the power to do so.
Are you waiting for Microsoft to launch a "slim" Xbox One before buying it?