If you're still rocking a handset running Windows Phone 8.1, it is important to note that mainstream support for the operating system is ending tomorrow, as Microsoft previously announced. Prior to the availability of Windows 10 Mobile for select handsets, the last major update to Windows Phone 8.1 was Lumia Denim, which started rolling out way back in December 2014.
Some Windows Phone 8.1 handsets have been offered an upgrade path to Windows 10 Mobile for the past 16 months, but Microsoft hasn't exactly been pushing users to do so. As Neowin noted earlier, the company didn't exactly inform users that it was available. Instead, you had to be aware of it, and go to the Store to download the Upgrade Advisor app, which would then determine if your handset was eligible for the update.
Lifecycle support date for Windows Phone 8.1 began on June 24, 2014, with Microsoft promising three years of support, which includes security updates. The firm stated that:
Microsoft will make updates available for the Operating System, including security updates, for a minimum of 36 months after the lifecycle start date. These updates will be incremental, with each update built on the update that preceded it. Customers need to install each update in order to remain supported. The distribution of these incremental updates may be controlled by the mobile operator or the phone manufacturer from which you purchased your phone, and installation will require that your phone have any prior updates. Update availability will also vary by country, region, and hardware capabilities.
According to the latest statistics from AdDuplex, 73.9% of Windows phone users are running Windows Phone 8.1, and only 20.3% are using Windows 10 Mobile. This essentially means that if Microsoft does not extend the lifecycle support date, a majority of current Windows phone users will be utilizing unsupported handsets.
It is important to note that Microsoft hasn't offered an extended support date, if any, as of yet. We have reached out to the company to inquire as to whether extended support will be provided, and if it will still offer existing upgrade paths after July 11. We'll let you know if we receive a response.