The personal computer isn't dying, but its days of dominance are numbered. Research firm IDC predicts the number of U.S. mobile Internet users will surpass their wired counterparts by 2015.

As smartphones outsell feature phones, and tablet sales boom, mobile devices in the U.S. will become the preferred means of Internet access within four years. By comparison, the number of users going online via PCs "will first stagnate and then slowly decline," IDC said in a statement.

The mobile migration will begin in the U.S., with Western Europe and Japan soon to follow.

A boom in the number of global Internet users will transform the online world as well. IDC predicts 40 percent of the world's population, or 2.7 billion people, will have access to the Internet by 2015--up from 2 billion in 2010.

Advertisers, naturally, will follow the crowds. Worldwide online advertising will nearly double from $70 billion in 2010 to $138 billion in 2015, IDC forecasts.

So does this mean the post-PC era is underway? Not exactly. With PC manufacturers selling hundreds of millions of personal computers each year, it's still a stretch to say the PC is dying. It's not even sickly, in fact.

Then again, a surging number of Internet users will be perfectly happy using a phone or tablet to go online, and may never need--or perhaps be able to afford--a conventional desktop or laptop PC.

Contact Jeff Bertolucci via Twitter (@jbertolucci) or at jbertolucci.blogspot.com.