A mock up of what the Xbox partner handheld could look like, we believe to be codenamed "Keenan." (Image credit: Windows Central) (Image credit: Windows Central)Here's your first glimpse at Xbox's next-gen hardware plans, and some parts are being executed more quickly than you might think.The Xbox Series X|S generation has been a bit of an odd one. Microsoft's Xbox console hardware sell-through has declined quarter over quarter for some time, but Xbox's addressable monthly active user base has b...