1. In my CPE courses I typically discuss what WiMax technology can do, and this technology is commercially available now, in a limited form. The main problem is that WiMax uses commissioned frequencies, not free frequencies like other Wi-Fi devices. That means the government charges people for broadcasting on WiMax frequencies, so there is a different pricing model in regards to WiMax.
2. In other parts of the world, we already see WiMax in place like you are seeking. For example, this WiMax router available in Korea will get the job done - http://www.ubergizmo.com/2007/02/long-range-wifi-router/
3. The commercially available WiMax devices offered by service providers here in the US are currently limited in distance and users. These service providers have the ability to control the range of a WiMax device, and for right now, they are limiting this range to just 150 feet, as discussed in this example: http://cradlepoint.com/products/ctr500-mobile-broadband-router# under the features tab near the bottom of the page.
4. Here is an example of a WiMax router that uses the free frequencies, and therefore does not offer the same range as WiMax routers using the 2.3 to 2.7 Ghz pay frequencies. http://www.calamp.com/products/private-wide-area-networks/ip-modems-a-routers/220-sentry-4g-series The range limitation of this device is not reported, but the 900 Ghz frequency is limited in range.
5. You can read an extensive technical description of WiMax here: http://en.wikipedia.org/wiki/WiMAX.
6. This page explains the following limitations related to WiMax:
7.
This page also confirms that WiMax
is able to effectively transmit at speeds up to 1000 MBs -
8.
This page also confirms that WiMax has a maximum reach of
a 25 mile radius, about 17.6 miles if at ground level due to the curvature
of the earth.
9.
This page also confirms what I said about data
speeds of up to about 30 MBs per second as a practicality. 
10. Here is a 2008 article discussing WiMax implementations of up to 10 mile radius. http://happyrouter.com/what-is-the-longest-range-wifi-wireless-gear-you-can-buy
11. Here are some example offerings b WiMax service providers.
http://hothardware.com/News/Sprint-Ups-The-Ante-With-WiMAXCapable-WWAN-Routers/
http://gadgetauto.com/wimax-router-with-integrated-wifi-price-specs-picture.html
12. In the presentation I predicted that WiMax devices with greater range will become more commercially available. For example, here is a WiMax router offered by NetGear http://www.netgear.com/service-provider/products/mobile-broadband/3g-4g-mobile-broadband/MBR2000.aspx, but the range limitation for this device is not reported.
Keep looking for this technology to expand in the future here in the US.