MS_Nerd noticed an interesting note on the hardware specifications page for Windows Phone that simply reads
"Additional sensors, such as proximity and light, are on the phone but are not available for developer interaction yet."
Of course the key word there is "yet" which certainly implies that Microsoft will be further opening up dev tools to more advanced features on the phone. Such access will of course allow some more interactive software and hopefully spur developer creativity, resulting in light-sensitive apps or ones that use the proximity sensor as a trigger for an alarm, etc. Perhaps we shouldn't see this too much as a surprise. Microsoft built smart developer APIs for the other sensors, so it is just a matter of time before they expand it other areas. Seems obvious.
Also of interesting note is although Windows Phone OEMs could drop the camera, MS_Nerd in our opinion correctly suggests that this was more for government and enterprise reasons than consumer. It's very standard that a requirement for government issued phones or for those working in certain areas of enterprise don't have cameras on their devices to prevent espionage. BlackBerry, Treos of yore and even Windows Mobile devices commonly had variants where the camera was removed from the device and there's no reason to believe that Microsoft wouldn't want to have their phones in this specialized area as well.
Source: MSDN; MS_Nerd