Not that far fetched. Design was finalised before release so E3 or Fall 2015 is a solid 2.5-3 years and 1.5-2 years for consumers.
Then there is this.
Chip designer AMD has developed a smaller, more cost-effective 20nm version of the main processor found in Xbox One, opening the door to a cheaper 'slim' version of the Microsoft console. The news comes from the LinkedIn bio of AMD's senior manager of SOC (system on chip) physical design, as discovered by Mosen from the Beyond3D forums. The entry in question says 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."
http://www.eurogamer.net/articles/d...aper-cooler-xbox-one-processor-in-development
"However, with the cost-reduced design of the main Xbox One processor complete, production economics are the only thing stopping Microsoft from creating a 20nm-powered 'Xbox One Slim' right now. Newer chip fabrication technologies are notoriously expensive in their early years as the number of usable processors gleaned from each silicon wafer (the "yield") is very low. There's also a question of capacity. Right now, it's believed that the majority of TSMC's 20nm production line is occupied creating the A8 and A8X processors used in the iPhone 6, 6 Plus and iPad Air 2. Behind Apple, AMD and Nvidia are waiting for access to 20nm technology in order to power their next-gen PC graphics cards, due in 2015."
If Microsoft can save money with a slim, they'll do it. I don't think a certain time gap has too much to do with it.