>Yes, going forward, the number of modems/radio interfaces available for backhaul on a device is seemingly always increasing (GSM/GPRS/EDGE, Bluetooth, W-CDMA/HSDPA, 802.11b/g, LTE...), but on a phone the GSM Um is going to be present for a very long time virtually anywhere in the world (except in Japan).
Not likely. AMPS/DAMPS died quickly with the advent of GSM/CDMA, for example (oh, sure there were few holdouts). Once we have viable 4G standards, they're going to spread quickly. There are just too many advantages: cheaper roaming, better data integration, more bandwidth, less power consumption, etc.
>Instead of thinking about the costs of initial hardware certification, consider instead every business case that you may have encountered (in designing networks) where a mast had been planned but wasn't economically viable based on the threshold of subscribers in that area.
Almost never happens. Even at $1 ARPU per month it's economically viable to install a tower even with 50 subscribers. You don't really get lower than that. And if you DO get lower, than most of your investment will be spent on getting uplink anyway (usually a microwave link, which requires, you guessed it, a tower for line-of-sight).