Industry experts in tech capital Taiwan are expecting the sales volume of built-in 3G modules to exceed those of 3G USB modems and similar external devices by the time 2012 rolls around. Sales of internal 3G modems are expected to grow by 30% year-on-year in the next three years.
This comes from a push by vendors to include 3G capability in almost all mobile devices from eBook readers to slate tablets and netbooks. We've seen more and more devices getting cellular wireless internet like the Kindle and iPod Touch.
Though this might signal the end for USB 3G modems, they still have their use. USB devices are more mobile so you can use it in a jiff if your regular connection conks out. It also can be shared between netbooks and other devices, though more people are turning to MiFi mobile wireless hotspots for this function.
In my part of the world, these devices are still popular since it's the quickest way to get portable Internet without getting a new device.
source Digitimes
A post from the Asus Eee PC blog.
USB 3G modems sales being overtaken by built-in 3G modules