A random thought today: UMTS 900, the 3G variant running in the 900 MHz band so far mostly used for GSM is already used in a couple of countries like Finland and France to get 3G coverage to rural areas. Mobile devices for this frequency like from Nokia are also on the market already. The big difficulty with UMTS 900 is to find enough space in the narrow 900 MHz band for the 5 MHz carriers. However, I guess that is mostly an issue in cities and not so much for sparsely populated areas, like for example the Scottish highlands, where only a few GSM carriers are in active use and base stations are spaced 7 km apart or even more.
I know, the UK has so far not allowed the use of 3G in the 900 MHz band due to open market questions, but from a user's point of view I think it would be a great thing. In the mid and long term, however, I think the 900 MHz band will be opened up for other technologies, as even in cities, 3G and also LTE have/will have the big disadvantage compared to GSM of a much inferior in-house coverage. Going from a voice centric to an IP centric wireless network architecture, it seems like a natural evolution of things.