I’m buying the maximum (6).
Hopefully we can get a v2 version of the thermostat that will be able to handle a lot more than 6 in the future. That way we can put one in every bedroom, and every major room (living room, dining room, den/family room, kitchen(s), office, have 1 outside for easy viewing even though it says not to, etc. 
A nice work around will be to enable allowing the HMS climate sensors’ data to be accessed by the thermostat, since the HMS hub can hold a ton of sensors.
These are extremely nice looking sensors with long battery life! I know they could’ve been a lot cheaper if you left off the display screen, etc, but I’m glad you made some really high quality, good looking ones here.