Nokia is planning to update existing Windows Phone 8 devices to 8.1, under its Lumia Cyan branding, with additional features specific to its smartphones.
According to an image from @evleaks, Nokia is planning to finish the update in late June or early July for its existing devices, beginning with the Lumia 1020 and 1520, followed the next week by the Lumia 920 and other older devices like the 620, 520 and others. A couple of weeks later, in the third week of July, continuing to early August, the company will begin the over-the-air rollout.
Unfortunately, the image depicts timelines for the Belgium, Netherlands and Luxembourg region, which is likely earlier than North America, and does not take into account carriers. While Windows Phone 8.1 will be rolling out before the end of the summer, the updates themselves are still subject to carrier approval, which usually adds a few weeks to each tally.
The good news, though, is that all Windows Phone 8 devices, even the oldest ones like the Lumia 520, will be upgraded.