The thing I seem to remember is that microsoft never declared any dates for releasing updates like the cyan or denim update. I doubt they ever wrote that, for instance, Tanzanian lumia 920 users will receive the cyan update on 24th July 2014. Or Indian lumia 520 users will receive denim update on 25th Nov 2014. Or Polish lumia 1020 users will receive the denim update on 20th Dec 2014
They always wrote that "the name" update will start rolling out in the next few months to select regions around the world. This will be a steady rollout expected to start in quarter 1. Never mind that the actual number of devices that receive that update in quarter 1 represents 5% of the global windows phone users.
This is my prediction:
Windows 10 mobile will start rolling out from late February to the first wave of devices for less than a dozen countries which would most likely be US, Finland, China, UK, Germany, Spain, France, India, Thailand, Australia, Italy and Philippines.
From May to September, Majority of worldwide users will receive the new OS for most of the first wave devices. This includes most of Europe, Asia, Africa and South America. Stubborn US carriers might also be releasing at this time
From August to December 2016, a new wave of devices will start receiving the W10M update such as the 20 series like 1020 and 520. Again this will be for a few countries at first followed by the majority of the world months later, going on until early 2017
If by March 2017 your device hasn't officially received the update, then know that either Microsoft or the local cellular company have forgotten that you own a windows phone and by that time there's no chance of getting the update officially.
Am I being pessimistic? Not really, just basing on past experience. 14 months down the line and there are countries and devices that still haven't received the denim update. So I can expect the same to happen again with W10M
And if you don't have the denim update for your phone, then tough luck as there won't be any W10M for you officially