When will this be available?
I'm not aware of any plans for a minute granularity in Data Warehouse. However, minute-by-minute traffic is available in Analysis Workspace.
You are welcome to create a thread at ideas.omniture.com so we can keep track of this enhancement request.
This is really a pity! Since technically it is already there. But you cannot meaningfully analyze the data by minutes in analysis workspace, since the range you can look at is quite limited!