Mifi is available in the UK it is aimed squarely at the consumer market here. I looked it up. The trademark is apparently owned by 3UK a mobile SP with not alot of their own infrastructire. I assume thats the UK trademark and they ase an Huawei product.
Not sure if it will ever be mainstream? Worth knowing about as a rogue no doubt.
As for most Cisco 802.11n deployments being 5.0GHz I am not seeing a great deal of 802.11n uptake at present. People who are installing are putting in a/b/g but I guess thats the economy. Those installing "n" are still very much using 2.4GHz. I know certainly on larger deployments there is still alot of legacy stuff and thats for 2.4GHz although its generally all g capable.
Cisco do have bandselect which deleys association to the 2.4GHz spectrum to try and get clients onto the 5.)GHz network.