It is definitely here to stay. Guarantee it.
The benefits of Atmos over TrueHD
CAN BE a lot more significant than TrueHD over DD.
There are some Atmos, DTSX, and Auro3D movies that don't seem to have much enhancements over DD or DTS. But there are plenty of Atmos/DTSX movies that are pretty awesome vs DD and DTS.
Like VonMagnum says, since it is backward compatible with Dolby Digital just like Dolby TrueHD is backward compatible, there is no reason to change it until they find an "enhancement" for Dolby Atmos.
Like how Dolby Atmos is an enhancement for Dolby TrueHD. But TrueHD is still around since Atmos --> TrueHD --> Dolby Digital are all backward compatible.
Let's say they did find an enhancement for Atmos -- let's call it AtmosMAX. Then we would still have Atmos: AtmosMAX --> Atmos --> TrueHD --> Dolby Digital are all compatible.
Same thing with DTSX --> DTS-HDMA --> DTS backward compatibility.
So Atmos is here to stay.