Microsoft has officially declared that it will support Surface with Windows RT for four years. April 11, 2017 is the date when the mainstream support will be discontinued. That means Surface with Windows RT buyers can expect security fixes and other updates to Windows RT and the included Office Home and Student 2013 software until at least April 2017.
Normally, Microsoft supports consumer and business versions of Windows operating systems for five years (mainstream support) and the business versions gets an additional five years of extended support.
View: Microsoft Support page
Source: Zdnet