Asymco analyst Horace Dediu claims that the success of iPhone and iPad devices will see the Cupertino-based firm reach a "parity" with its rival by 2014.
PCs currently sell approximately 19 times more units than Apple Macs, but this figure has declined from 54 times as many in 2004.
"If we consider all the devices Apple sells, the whittling becomes even more significant and the multiple drops to below two. Seen this way, post-PC devices wiped out of leverage faster than it was originally built," said Dediu.
"They not only reversed the advantage but cancelled it altogether. Considering the near future, it's safe to expect a 'parity' of iOS plus OS X versus Windows within one or two years. The install base may remain larger for some time longer but the sales rate of alternatives will swamp it in due course."
Dediu went on to say that the knock-on effect of this would likely see Microsoft Windows face a struggle to remain as the default platform across numerous industry sectors.
Microsoft recently announced plans to challenge Apple in the tablet market with the launch of its Surface slate. It will also take on the firm in the smartphone OS market with its next-generation Windows Phone 8.