It annoys me that people keep spouting this FUD, that if AT&T doesn't buy T-Mobile there are no other potential major bidders T-Mobile may break up and sell off assets piece-by-piece or shutdown completely.
Off the top of my head I can see multiple potential bidders for T-Mobile at the right price (not the AT&T "I am rebuilding my monopoly price").
For example it would make sense for both Telefónica (which already has a major presence in the Americas) or América Móvil (which also has a major presence in the Americas, with almost twice as many subscribers in Mexico as T-Mobile has in the United States. Both could find strong synergies in buying T-Mobile, up selling additional services to the Hispanic community.
Vodafone as well has long wanted to use their own brand in the United States (especially since they are only a minority shareholder in Verizon wireless). The could sell their Verizon Wireless stake and use the money to buy T-Mobile.
It could even make sense for China Telecom as they already plan to launch Wireless Service in the USA next year.
I am sure I am just scratching the surface of potential bidders so please, please stop the "OMG, T-Mobile will shut down if AT&T doesn't buy them" FUD.