Understood, but that is because its a licensed spectrum in contrast to DECT, BlueTooth or WiFi.

Thats a moot point. There are all kind of backward compatibilities. You were able to use GPRS 5 years ago, and you'll be able to use GPRS in 5 years, too. The same is true for the popular implementations of 3G. Yes, you never know. A telco could go kaboom. We might enter in a Great Depression, or a war, or a black hole... but these networks were rolled out with major infrastructure investments.

If you'd argue: well, soon 4G is out, and my current $device can't use that, yes, you have a valid point. However new != better, and this is an inherent feature of hardware, and also true for USB 3.0, BlueTooth 3.0, 4G, WiFi 802.11i, WiFi 802.11g, and so on. Its even more an inherent feature of embedded hardware.

To mitigate this the Sharp Zaurus had a CF and a SD card. However, on-board storage was minimal (except C3x00 series), and it did not have on-board WiFi, BlueTooth, or GPS. Most Zaurus users ended up with a SD card for storage, and a CF card for WiFi (only supporting 802.11a/b). While there were CF cards providing GPS you couldn't use them because you already needed a WiFi card.

On a NIT this is potentially different because a NIT already has BlueTooth, WiFi and the N810 even GPS. However in this Age you can't expect users to carry around all kind of devices, batteries, cables, and so on. The default ones are already more than enough. That makes a USB 3G not a good option although it'd use about 400-500 mA while in use, and about 70 mA when idle (can be disabled too, ofcourse). So, if the NIT would have CF, PCMCIA, or USB (normal connector) this'd open a wide perspective of possibilities. Add to that being able to power the device over USB, and the fact such USB controller shouldn't be wasting much space in contrast to PCMCIA or CF.