This is the wrong forum, but I'll answer anyway.
AX is not going anywhere right now and if anyone says otherwise they're wrong. What you're probably hearing is Microsoft is ending support of the 2012 version in 2021...that's because they have a newer version out. It's equivalent to ending support of Windows 7 because we're on Windows 10 now.
These are the main active versions of AX in order (gotta love their naming conventions):
- AX 4.0 (Support has ended)
- AX 2009 (Support ends 2018)
- AX 2012 (Support ends 2021)
- Dynamics 365 for Operations
Dynamics 365 for Operations (aka D365fo aka D3fo) is the latest version and Microsoft is putting tons of weight and development into it. The core of it is still developed in X++. I also predict it will be the last version of AX and support will not end.
Dynamics NAV however I know very little on, but I believe NAV is being replaced with Dynamics 365 for Financials, which was formerly called "Project Madera", which was based on NAV. I could be wrong here and maybe D365 for Financial is the cloud version and NAV is the on-prem version. I don't know honestly.