It would have to be thought out well and not just on a whim. Nintendo progressed from real games to digitised versions of said games before any real computer games were made by it, Sony was hired by Nintendo to make a disc system but had a falling out and didnt want to waste the technology (similar origins as the Phillips CDi) Microsoft bought a lot of companies and monopolised their way in as well as having PC only titles for some time they could continue onto its console.
Apple would need to bulk up its Mac gaming platform before even thinking about making a successful console. The myth about over priced hardware (actually the just dont make low end consumer junk and cost similar to GOOD PCs) even if true for a gaming console wouldnt deter it (look at the PS3s launch prices) though its most successful games platform was marketed as a phone (iPhone/iPod Touch apps)
Maybe in the next generation Apple COULD make a console and may have enough 3rd party game support but i dont see it happening as it would dilute the company's attentions.