People are growing increasingly jaded with OSX and Windows, both of which lack a passionate visionary and are becoming increasingly bloated and making weird UX choices.
I do not mean making a retro device, or even playing off of some modern variant of AmigaOS, I mean rethinking/resurrecting the brand the same way Jobs did when he returned to Apple.
It would not necessarily mean completely reinventing hardware or software. Apple's switch to a BSD-based OS and Intel chips was an example of how you can build a great computer on top of existing hardware and software.
The Mac has no "real" competitors - that is, companies which manufacture both their own hardware and software to produce desktops (other than consoles, which are not really desktop replacements).
Anyhow, it is obviously no small undertaking, but I refuse to believe there should only be two mainstream choices out there for desktops, or that the space for innovation is dead (more so on the software/coding/UX side).