AT&T is also rolling out a 10x10 configuration in markets that they can thanks to the acquisition of the Qualcomm 700 MHz spectrum. Everywhere else AT&T plans to launch a 5x5 configuration at 700 MHz.
Tmobile is planning to rollout LTE in 2013 and they are planning on a 10x10 configuration on their AWS spectrum in their top 25-50 markets. I would assume for the rest of the markets it would use a 5x5 configuration.
T-Mobile has no plans to roll out nationwide 4G LTE only has plans for top 50 markets. Also they will only be 5x5 configuration because most spectrum is being devoted to HSPA+42 and HSPA+84 which have speeds equivalent to 4G LTE. I personally believe T-Mobile should just role out HSPA+42 and HSPA+84 which will actually be faster then ATT and Verizon's 4G LTE Netowrk because T-Mobile has less customers and we have already seen in comparisons between HSPA+42 on T-Mobile and ATT's 4G LTE are almost equivalent in speeds.