The Kinect port is pretty fast I think, but I don't think it's fast enough (I can't actually find the speed of the proprietary Kinect 2.0 port anywhere). To transfer the amounts of data that you'd need to release external hardware expansions, a console would need a Thunderbolt port I think. Thunderbolt 1, 2, and 3 are capable of transfering data at 10 Gbit/s, 20 Gbit/s and 40 Gbit/s; In order to boost both the CPU and GPU you'd need at least a Thunderbolt 1 port I think, maybe even Thunderbolt 2. I don't think there's any way around releasing a new console if MS wants to do this upgrading thing. 

The best thing they can do right now I think is to improve the Windows Store as much as possible while continuing to support XB1 as much as they can. Windows Store needs alot of work to catch up to Steam, right now it's mainly indies and ports of Windows Phone games. MS needs to get more AA/AAA 3rd party devs/publishers to release in the Store. They need to allow gamers to access the file folders for Windows Store games, with accesss to file folders currently restricted there's no way to mod Windows Store games. They need to allow borderless fullscreen play on Windows Store games (currently fullscreen isn't truly fullscreen). They need to prepare a format for fairly frequent large sales, like Steam has. I'd say they have a good 3 years still to do all that before Sony is probably ready to release PS5. Then MS can release Xbox 4, which is built to be upgradeable from the start, and has full access to all Windows Store games, existing and future. They can sell upgrades in little cases that are made to match the style of the main console, that connect to a thunderbolt port on the outside of the console and sit flush with the console, something like this 3rd party designed hard drive enclosure for XB1, except bigger: http://www.amazon.com/Collective-Minds-Drive-Enclosure-Front-Ports/dp/B00T76ZGDO/ref=sr_1_1?s=videogames&ie=UTF8&qid=1457026167&sr=1-1&keywords=xbox+one+hard+drive+enclosure

Speaking of Platformers, give me Battleblock 2

Also Conker or Banjo... MS give me something!

Careful what you wish for...

Yeah, that's what I'm thinking too, something like this, upgrades that connect to port on the side that match the style of the case:

http://www.amazon.com/Collective-Minds-Drive-Enclosure-Front-Ports/dp/B00T76ZGDO/ref=sr_1_1?s=videogames&ie=UTF8&qid=1457026167&sr=1-1&keywords=xbox+one+hard+drive+enclosure

Here's the scenario as I see it:

Xbox 4 releases let's say Holiday 2019 in 3 versions; base, premium, and enthusiast. Base is $400, has a 4 core (8 thread) AMD Zen CPU, 8GB of DDR4, a 4500 gflop AMD GPU, and a 2TB hard drive; goal is 1080p 60 fps with enhanced graphics over XB1 games. Premium is $700 and has a 6 core (12 thread) AMD Zen CPU, 16 GB of DDR4, a 7000 gflop GPU, a 2 TB hard drive, and a 250 GB SSD; goal is 1440p 60fps. Enthusiast is $1200 and has an 8 core (16 thread) AMD Zen CPU, 32 GB of DDR4, a 10,000 gflop GPU, a 3 TB hard drive, and 500 GB SSD; goal is 4k 60 fps.

 The system runs Windows 10 (or 11 if it's out by then), and has full access to all Windows Store games (past, present, and future). The base system comes with a controller and a mini touchpad keyboard for navigating the PC features. You can also play with a gaming mouse and keyboard, and MS might even offer their own gaming lapboard for those who prefer mouse and keyboard.

The case comes in 3 parts, the middle part houses the motherboard, CPU, CPU cooler, RAM, bluray drive, and power supply; and the bluray drive and power supply come in little slots that can be easily slid out of the front and back of the console respectively. The left part is a removable hard drive enclosure like the one I linked above. The right part is an enclosure that houses a graphics card that connects to a Thunderbolt 2 port.

The above scenario would make the Xbox 4 highly upgradeable. You want a new GPU, you can simply remove the GPU enclosure and go to your local Gamestop and trade-in the old one for a new GPU that comes in it's own enclosure. You want a new CPU and RAM, you can slide out the bluray drive and power supply from the center unit, and go trade it in for a new center unit that houses a better CPU and more/faster RAM, then slide your old bluray drive and power supply into the new unit (saving you money from needing to buy a new PSU and bluray drive as well since they're components that don't really need to be upgraded very often). You want a bigger hard drive, you simply remove the hard drive enclousure and trade it in for a new one that already comes with a bigger hard drive.

ALAN WAKE'S RETURN TRADEMARK IS NOT FOR A GAME