I don't think you can assume zero moisture in it though even if you don't have water
A camera will tend to attract moisture like anything else and once warm this moisture will release in the housing increasing humidity this may be a much more prevailing effect than removing the gas from the housing
This also reconciles the housing in the sun scenario with subsequent fogging
Generally it is impossible to determine the effect of vacuum in terms of condensation as the moisture in the camera is unknown. There could or not be a benefit depending on the temperature of the air, the air relative humidity and how those interact but this could or not improve matters
In essence I would say that camera and housing preparation for what I am concerned stay the same and keep hoping for the best!!!
Edited by Interceptor121, 03 April 2014 - 11:36 PM.