A bug report page on the Tizen project website has confirmed that Japanese carrier NTT DoCoMo has a Tizen smartphone in the making, sporting the model number SGH-N055 (it's strange Samsung is using SGH as a model number on Tizen, something that could cause confusion with the company's Android devices). The device was mentioned by a user on the bug report's comments section, saying that “SGH-N055, docomo version, does not have this bug,” indicating the device is already under testing by some parties.
A report earlier today hinted at an October unveiling of the first Tizen smartphone in five countries including Japan, so it is very likely we will see the SGH-N055 get announced at Samsung's developer conference, with perhaps a launch in November or December. The specs remain unknown, but DoCoMo will probably have a few unique features of its own onboard, apart from whatever Tizen itself offers.