In 2010, Microsoft announced a bold, company-wide initiative to re-brand their design language based on Metro traffic signs. The idea was to stress content over chrome. To be authentically digital. No fake leather. No bevels. Just you, your stuff, and fluid motion to give you context of where everything was.
Today, Apple announced iOS 7; a dramatic departure from their previous design language. It will be available in the Fall of 2013.
Notes: The Windows Phone featured (Lumia 920) was not released until 2012, but the design language is the same as it always has been. Windows Phone was released in 2010, but the multi-tasking UI was not copied from WebOS and released until 2011.