When is The End of Life of Windows 7 Operating System?
Microsoft announced that the company will stop all feature development, security patches, and technical support this coming January 14th 2020. Which results that after January 14 2020 if an issue is detected, or a security exploit is discovered for this Operating System, you might contact Microsoft technical support but there will be no fix for your request. Windows 7 will be then declared obsolete by his own creator.
Will Windows 7 stop working?
Absolutely not, but it will become risky to connect those PC’s to the internet, new versions of software won’t be recommended to install on it, even antivirus will stop protecting this version of operating system. Status Quo can be preserved at your own risk with complete isolation from other systems that are up to date, if this makes sense for your business. (I have seen very few scenarios where this does make sense). But in general for office and production environments you want to start rolling up your sleeves in order to deploy Windows 10 before January 14 2020.
For more detailed information you can read Microsoft article here