updated 08:53 am EDT, Mon March 18, 2013
Update period could be extended past initial 18 months
Microsoft will stop supporting Windows Phone 8 and Windows Phone 7.8 in mid-2014, according to a product support lifecycle table. Updates, including those to help secure the mobile operating systems, will last until July 8, 2014 for Windows Phone 8, while Windows Phone 7.8 users will see its life cycle support continue until the 9th of September.
The table explains that the updates will be available for an 18-month period after the cycle commences. WM Power User notes that this would in theory mean that a Windows Phone 8 device sold in July of this year would receive only one year of guaranteed software updates. A further note on each WP listing states "Distribution of the updates may be controlled by the mobile operator or the phone manufacturer from which you purchased your phone. Update availability will also vary by country, region, and hardware capabilities."
The 18-month period of support is a minimum time period, and not a definite date for when Microsoft will cease all developments on the platform. Microsoft has previously extended support for Windows Vista and 7 to a maximum of ten years, rather than the five initially offered for retail releases. Though that extension was for software operating on computers, it is entirely possible that Microsoft could likewise extend the WP 8 and WP 7.8 support time further than 18 months.
It is rumored that Microsoft is heading towards a quicker product release cycle in both desktops and the mobile OS space, with its Windows Blue and Windows Phone Blue initiative. The two Blue iterations are expected to offer users new features inside larger updates, as well as integrating the two platforms together. It isn't clear if the next version of Windows Phone, due by the holiday season, will be a part of the Blue initiative.