Unity 8 will offer the traditional desktop interface when it detects a desktop. The same OS will switch to a touch-based interface on touch-based devices such as tablets and smartphones.
Microsoft's approach with Windows, and backward compatibility in general, is commendable. "Users can install new versions of this OS on old machines, sometimes built on a mishmash of components, and still have it work well. This is a remarkable feat of engineering. It also comes with limitations — as it forces Microsoft to operate in the past." But Apple doesn't share this focus on interoperability or legacy. "They restrict hardware options, so they can build around a smaller number of specs. Old hardware is often left behind (turn on a first-generation iPad, and witness the sluggishness). Meanwhile, dying conventions are proactively euthanized," says Karjaluoto. "When Macs no longer shipped with floppy drives, many felt baffled. This same experience occurred when a disk (CD/DVD) reader no longer came standard." In spite of the grumblings of many, Karjaluoto doesn't recall many such changes that we didn't later look upon as the right choice.