Ala Saddam.
This is reported as an official statement by Sistani, which is rare for him to be direct and public on big issues. I doubt that such a statement would be issued without a lot of analysis and discussion first.
Perhaps there is a replacement for Maliki in the wings, who now has Sistani’s informal backing.
Only a new Prime Minister could avoid a continued bloodbath in Iraq, but no Prime Minister will be able to resolve things quickly. The big thing that a new PM might deliver is a deal with some major Sunni and/or Kurdish faction. They will still have to fight ISIS/Turkey/Qatar.