Depends on application type and device.
I wouldn't hold my breath, e.g. in games - one of the most performance-critical apps - the best idea so far is to spin one thread for physics, one thread per AI, one thread per game logic etc.
Here is a good blog post describing how sad the things is: http://bitsquid.blogspot.co.uk/2015/03/multithreaded-gamepla...