Hello,
if you are evaluating Alfresco Cloud for your company as a potentially upgraded account (more than just the free service), I would suggest you get in contact with the local Sales contact or a local Alfresco partner to support your evaluation. It may be possible to provide a limited-time trial of some of the extended features of the cloud service and you have someone handy who can better answer road map questions.
In terms of road map, Granular Permissions were originally scheduled for the first half of this year. Since Alfresco has a pretty massive product road map for 2012, some features are bound to be shifted. At the moment, I don't know of a more concrete plan than mid- to late 2nd half of 2012. In terms of how this feature will play out, I think the best way to get to that information would be via direct contact - all Alfresco Sales reps have local pre-sales technical support staff that can answer these types of questions.
Technically, all of the features you inquired about are already possible in the Alfresco product - most of what is missing would be the granular / intuitive UI within the Sites concept. In case some of the features may not be exposed in the cloud offering, one of the coming enhancements (Public API) will make it possible to put a custom UI in front of the cloud while still having all the data / backend infrastructure managed by Alfresco.
Regards
Axel