Not to cause you any grief, but I replied "yes" to my Japan tentative acceptance and they responded with instructions (like get a passport if you don't have one, keep these dates open, etc.). It's possible that they're just getting backed up with emails so I don't know if you should really be concerned (and I really don't want to cause you to panic). However, if the wait becomes unberable (as it probably would be for me), maybe you could send them a question to prompt some sort of response/communication?