Just to clarify, when we initially release R81, the "SP" version won't be available immediately.
It is planned for around the same time the first R81 JHF is released.
It should be a shorter wait than 3-6 months. 🙂
Other than anything directly related to scalability/distribution/clustering, R81SP will use the same code as regular gateways.
JHFs between R81 and R81SP will be basically the same released around the same time.
Other limitations that apply in SP code will be in sk148074.
Eventually (in a later release), we will have a unified ISO for regular gateways and Maestro/Scalable Platforms.
As for your specific question, Updatable Objects in HTTPS Inspection policy is an R80.40 Gateway/Management feature.
This means R81SP is expected to have it also.