On the 6th September 2018, Microsoft announced they would be supporting Windows 7 for an additional 3 years meaning that the official support will end in 2023. Although the support has been announced this does not mean everyone will be eligible. To get the extended support an annual per-device payment will be required which will increase each year, it is unknown what the pricing for this will be. Another condition to opt into the extended support is that you will need to be using a volume license key.
This is not the first time Microsoft has created a paid for update service for an operating system, it is the first time they have been so publically vocal about it. When they supported Windows XP with a similar service it was kept fairly quiet. A high fee was required to receive these updates and it is more than likely that the support for Windows 7 will be no different. It is currently unknown what fee for this support will be.
The extra three years of support should provide enough time for companies that are partners of the volume licensing program to move their systems over to Windows 10.
For more information on this subject, you can visit the official Microsoft article here.