I'm hopeful hierarchy support will be coming for many objects in Power View in upcoming releases. However, I'm told that hierarchy support for slicers is not currently planned. I feel this is an important feature. I would hope I could either drop a hierarchy onto the drop area for a slicer, or choose several other fields from a table. Then Power View would show me just the members in the top level in the hierarchy. When I click one member, it would drilldown to the members underneath the clicked member. This would save me from having to add six slicers next to each other to support filtering by a six level hierarchy.
I on the fence about whether I should be able to use fields from different tables as levels in the drilldown. If so, I would assume some sort of crossfiltering would be necessary so that only relevant members from the drilldown field would be shown based upon which member of the first field was clicked. The current limitation that hierarchies can only put fields from one table/dimension into levels is sometimes restricting. So this might be a welcome feature.
I would hope drilldown will appear in charts, tables, any any other new objects you add in the future like maps.