If it is in early adopter then I would expect it to go GA at some point for both SaaS and Managed. Keep in mind that Managed is always 2 weeks behind SaaS as well. You can always toss in a RFE to ensure that they are aware of the need for this feature in Managed,
There are no plans to support SCIM for Managed at the moment. This is first time I hear the requirement. What would you like to integrate with ?