Back in January, we learned that Windows 10 Mobile's release to older Lumia handsets was delayed and would likely take place in late-February. Microsoft had sent an email to its partners, presumably carriers and possible OEMs working on Windows 10 Mobile devices, confirming the delay.
On the official Microsoft Mexico Facebook page (spotted via Winphonemetro), a company representative mentioned that Windows 10 Mobile was set for release on the 29th of February. Keep in mind that sometimes these representatives are misinformed, so until we get an official announcement from Microsoft, we're labeling this as a rumor. We'll have more on this as it develops.
This of course does not apply to the Lumia 550, Lumia 950, and Lumia 950 XL, which already comes with Microsoft’s latest Windows 10 Mobile operating system. If you cant wait for the official roll out of the update, join the Windows Insider program (if your phone is eligible) and snag the latest build now!
Thanks for the tip, Nicholas!