As some of the people have already aware, Microsoft 7 will not receive any more security updates after 14th January 2020. However, Microsoft has recently announced that they will only be extended the security update until 2023 for Enterprise users. The extended will only take action if the users or customers have signed up for the ESU package.
Having been said above, the security update will only contain a critical and important bug that been identified by Microsoft and it will include any latest updates or patches that recently exploited to the user or customer.
Mircosoft has stated as below:
Although the end of support for Windows 7 is January 14, 2020, organizations can purchase ESU at any time during the three years that the offer is available. If an organization waits and purchases ESU for the first time in year two or year three, they will have to pay for the preceding years also. This is because the security updates that are offered under the ESU program are cumulative
As been mentioned by Microsoft on their website, they have advised the customer who is still using Mircosoft 7 to upgrade their Operating System to Microsoft 10 Enterprise. Nevertheless, Microsoft 7 still can be used after the End of Life date but the OS will expose to the latest vulnerabilities or bug.
Source Windows 7: End of Support & Extended Security Updates (Youtube)
For those want to upgrade to Mircosoft 10 and Outlook 365, you can follow the guide from Microsoft