Update extensions.md

Author: hirenshah1

articles/cloud-services-extended-support/extensions.md

@@ -12,6 +12,9 @@ ms.date: 07/24/2024
 
 # Extensions for Cloud Services (extended support)
 
+> [!IMPORTANT]
+> As of March 31, 2025, cloud Services (classic) is deprecated and will be fully retired on March 31, 2027. [Learn more](https://aka.ms/csesretirement) about this deprecation and [how to migrate](https://aka.ms/cses-retirement-march-2025).
+
 Extensions are small applications that provide post-deployment configuration and automation tasks on roles. For example, You can enable a Remote Desktop connection in your role during cloud service (extended support) deployment by using Remote Desktop Extension. 
 
 ## Key Vault Extension