When will the SDK for Air S2 be released? Can anyone say! Well thank you!

The only date that has been announced is 31 December 2021,  but thats only for Android.    IOS date is still TBD.   

From - https://developer.dji.com/user/roadmap/#msdk

Mobile SDK
Estimated Release Time: 2021-12-31
Version: 4.16 Android Version(iOS:To be determined))
New Features
Added support for DJI Mini SE
Confirmed

Supported Product: DJI Mini SE

Supported Platform: Android

Description：Added support for DJI Mini SE.

Added support for DJI Mini 2
Confirmed

Supported ProductJI Mini 2

Supported Platform: Android

Description：Added support for DJI Mini 2.

Added support for DJI Air 2S
Confirmed

Supported ProductJI Air 2S

Supported Platform: Android

Description：Added support for DJI Air 2S.

Added support for High-Res Grid photo to Matrice 300 RTK
Confirmed

Supported Product: Matrice 300 RTK

Supported Platform: Android

Description：Added support for High-Res Grid photo.

Added support for Smart Track to Matrice 300 RTK
Confirmed

Supported Product: Matrice 300 RTK

Supported Platform: Android

Description：Added support for Smart Track.

Thanks for sharing.  very interesting info in comments