This leaked image suggests that there's some credence to the various rumours about an Xbox One redesign.
Possible production notes for a redesigned Xbox One emerge
The image above, originally posted on NeoGAF, suggests the existence of the 'Xbox One Second Generation', a slimmer model that has been rumoured since 2014. FCC filings dug up earlier this month suggested something similar.
Take this with a grain of salt, of course - it's not entirely clear where this leaked image is coming from - but the mounting evidence suggests that an Xbox One revision is likely. Whether or not it will be line with the major revisions hinted at for the PlayStation 4 NEO remains to be seen.
The Xbox One originally released in November 2013. Aside from different colour schemes and larger hard-drives, subsequent releases of the console have not seen major revisions.