The NPS extension for Azure MFA is not deprecated and there are no upcoming deprecation plans that I'm aware of. Like you mentioned, the deprecation is only for Azure MFA Servicer on premises and beginning September 2024, Azure Multi-Factor Authentication Server deployments will no longer service multi-factor authentication (MFA) requests.
The NPS extension was created as a step to move towards Azure MFA and away from MFA Server.
The recommendation is to migrate to the NPS Extension and Azure MFA using the migration guide. https://learn.microsoft.com/en-us/azure/active-directory/authentication/how-to-migrate-mfa-server-to-azure-mfa-user-authentication
Let me know if this helps and if you have further questions.
If the information helped you, please Accept the answer. This will help us as well as others in the community who may be researching similar information.