According to ABI Research principal analyst Philip Solis, “the UMD market will still be small compared to the wireless handset market, but with a forecast revenue of nearly US$27 billion in 2013, it will certainly be significant.”

While netbooks account for about 90 percent of today’s UMD market, they will fall to a distant second place by 2013, while MID (Mobile Internet Device) shipments surge ahead to take nearly 68 percent of the market, with Ultra-mobile PCs (UMPCs) remaining a niche category -- at least according to ABI Research (more on a differing forecast in a moment).

To put the UMD market forecasts into perspective, the 2013 estimate of 200 million shipped devices is roughly the anticipated size of the worldwide laptop computer market.

“As this market enters its rapid growth phase and starts to evolve, we will see considerable experimentation with different distribution channels: some will sell direct from the manufacturer, some via retail outlets, and some through mobile operators who will subsidize them to encourage new data plan subscriptions," Solis says.

For a slightly different perspective, ThinkPanmure analyst Vijay Rakesh has trimmed estimates on Apple and Intel as he sees a slowdown in the laptop market, reports Barron's. He thinks the notebook segment is being eroded by the new “netbooks,” ultra small PCs from Acer, Asustek, MSI and Dell.

We believe the netbook market is starting to make inroads into the core notebook market as a more price-conscious consumer opts for the cheaper alternative,” he wrote in his Intel note this morning. Rakesh says that checks with retailers find that netbook sales are “swamping core notebook sales.”

The analyst says that Taiwan notebook manufacturers finds the same trend, “with netbooks ramping up while core notebooks are slowing down and potentially slowing down further” in the fourth quarter. Rakesh says that low-priced netbooks “could dent Macbook sales” as consumer become more price-conscious and the global economy slows.

“Our checks indicate that while Mac desktops and 3G iPhone sales have been doing well, the notebook market could be impacted in the peak back-to-school season” from the debut of netbooks from a number of manufacturers. He notes that the Street expects Mac notebook units to grow 15-19 percent sequentially in the fiscal fourth quarter ending September, but cautions that “a netbook share gain in the notebook market, with consumers preferring lower-priced netbooks in the back-to-school season, could imply that the 15 percent-plus growth in the Mac notebook is a high watermark.”

Of course, there is speculation that Apple will release a sub-$1,000 MacBook in the near future, so we'll see. I think the company will. And I also think we'll see Apple's version of a UMD or MID -- but not until early 2009.