The news is coming from Middle East where users of Lumia 535 are receiving the Upgrade prompts on their handsets, as what seems to be the possible Windows 10 Mobile upgrade. Owners in Egypt and Jordan, are the first to report with the build number possibly unknown. Check out the screenshots below:

Microsoft has been delaying the upgrade for about 3 months now, when the flagship Lumia 950 and 950 XL came to the market. There is no official announcement yet but we do hope the update to roll out to other countries too, soon!

Source: WMPU