Sony Xperia Z will build new model of phone witl dual-band support. New model will work on AT&T and T-mobile neworks. It will  support  bands: GSM850, GSM900, GSM1800, GSM1900, UMTS850 (B5), UMTS900 (B8), UMTS1700/2100 (B4), UMTS2100 (B1), LTE2100 (B1), LTE700 (B17), LTE850 (B5), LTE1700/2100 (B4).

Announce should be in April 2013.