We’ve decided to increase the length of our support lifecycle from 18 months to 36 months. Beginning with Windows Phone 8 we’ll make updates, including security updates, available for 36 months. These updates will be incremental, with each update built on the update that preceded it. The mobile operator or phone manufacturer may control the distribution of these incremental updates and update availability may also vary by country, region, and device hardware capabilities.
In addition to the longer support lifecycle, we will also be releasing an enterprise feature pack as an update to Windows Phone 8. This feature pack will provide IT departments with more control over Windows Phones and give their employees a fuller productivity experience. […] We plan to provide the feature pack as an update in the first half of 2014.