As explained, Windows 7 officially reaches EOL as of Jan 14, 2020.  By which time, there will no longer be security patches from Microsoft and that will expose your firm's and your clients' data to breaches.

If for nothing else, just based on the IR 2018-175 alone, you should really opt to upgrade whether or not ProSeries 2019 will still run on Windows 7 (unofficially).  See excerpt below:

"The Financial Services Modernization Act of 1999, also known as the Gramm-Leach-Bliley (GLB) Act, gives the Federal Trade Commission authority to set information safeguard regulations for various entities, including professional tax return preparers.

According to the FTC Safeguards Rule, tax return preparers must create and enact security plans to protect client data. Failure to do so may result in an FTC investigation. The IRS also may treat a violation of the FTC Safeguards Rule as a violation of IRS Revenue Procedure 2007-40, which sets the rules for tax professionals participating as an Authorized IRS e-file Provider."