The mobile eco-system is mostly diversified by mobile makers because of two things: consumer and carrier needs. The same thing goes for HTC One which will be available on almost all US carriers (bands) and of course they will be locked as usual.
When it comes to the Chinese market things are a bit different there, Asian consumers appreciate dual-SIM capabilities on their phones, reason why HTC will be making three new variants of HTC One — 802D, 802T and 802W, which will be heading to all three major Chinese carriers: China Unicom (WCDMA), China Mobile (TD-SCDMA) and China Telecom (CDMA). These models have been discovered on China’s official device approval database.
The third digit in these naming scheme apparently indicates towards dual-SIM capability of the device according to a leaked image shared on Weibo network (Chinese Twitter equivalent) showing HTC 80W with its back cover taken off revealing two SIM card slots.
legend:  – dual-SIM support
source Engadget (CN); Weibo