2017 Mac Pro
The only Apple device that is older than the Mac Mini is the Mac Pro. Apple has not updated this professional device in over three years.
The current Mac Pro is showing it's age as it struggles to keep up with the demands of professional users. There are times where the Mac Pro handles 4K video editing like a champ and other times it is a struggle to even preview 4k clips.
Tim Cook told employees that there are "great desktops" coming from Apple in late 2016 and in early 2017 the Apple CEO told shareholders that Apple is committed to professionals. Talk is cheap, but with these two comments combined, we expect to see Apple make movement on the 2017 Mac Pro