Traditional notebook PCs are expected to be outsold by tablets three-to-one within the next three years, less than a decade after Apple kicked off the post-PC revolution with the iPad.

The forecast comes in a Thursday report from market research firm NPD DisplaySearch, which predicts that businesses and consumers will be snapping up more than 450 million tablets per year by 2017.

Fueling the shift, NPD expects the average selling price of tablets to fall slightly — from $311 in 2014 to $296 in 2017 — as economies of scale make display production less costly and manufacturers move to smaller tablet sizes. Traditional PC makers will be forced to follow the trend, NPD believes, leading to even more savings for consumers thanks to increased competition.

According to NPD senior analyst Richard Shim, "momentum for the tablet PC market is in full swing as they have become the dominant mobile PC form factor. Competition is expected to increase as traditional notebook PC brands, including Lenovo, HP, and Dell update their product portfolios to emphasize tablet PCs."

Much of the growth is expected to be driven by emerging markets, which NPD predicts will account for more than 60 percent of mobile PC shipments by 2017. Those regions overwhelmingly prefer the tablet form factor already — traditional notebooks book just 30 percent of sales, with tablets taking the remainder.