Yes, on July 11th, 2017 support for Windows Phone 8.1 will finally end.
Ok, so not many of you are still using Windows Phone devices anymore, but this may matter for those of you who are. Like, say, if you've got several hundred in your organization.
What does support ending mean?
The end of support means that no new updates, including security updates, will be made available. The release of Windows 10 means that I doubt you were expecting any more updates anyway but if you're using these devices as part of running your business then a lack of security updates might be important. See the official support notes for more.
What if you are affected?
Update any impacted devices to Windows 10 Mobile if supported by the hardware. (See this guide from AAWP for how.) If not then you should start thinking about replacing that hardware. It's several years old now anyway.