Lumia Users running Windows Phone 8 now started feeling jealous with Lumia 625 or 925 because Microsoft has launched latest Cyan Update with Windows 8.1 but others are waiting since after the launch of Windows Phone 8.1.
I think, it will take a month or two more to reach this update on every users pocket. However, Microsoft has opened the gate for those who are waiting for update to track the Windows Phone 8.1 update. Note that while the page may say an update is available, it is still likely the update will take a number of weeks to reach all handsets in your region.
Checkout this link to see whether the update is available or not. Read below if you want to know whether you are aligible or not get the update and also how to update your Lumia to Windows 8.1
Tip! Try to use a Wi-Fi network to download the update and avoid mobile data transmission costs. Before going through the update, connect to a charger or make sure your phone has enough battery power (minimum 50%). You might also need to make enough space on your phone for the update (1.5GB free phone memory is recommended).
To check for available free space, go to Settings > storage check (storage sense).
Step 2. To view and to install the updates, tap the notification, and follow the steps shown on your phone. Either you can install the update immediately or postpone the update according to convenience.
Step 3. The update should take around 15-30 minutes(depending on your network speed), but a major update could take up to 2 hours to complete depending on your phone model.