I haven't seen any evidence of Task support in the Calendar app on the iPhone, so I wouldn't hold my breath. Tasks in many way have always been an afterthought even in iCal, so I'm not really all that surprised. With the robust set of task management apps like OmniFocus it's probably not all that necessary either.
As for background location services, battery drain wouldn't necessarily be an issue, as the background process is supposed to use a low-power cellular-only mode when not running. From what I understand, it monitors the available cell towers and only does a detailed location update when that information changes. as I posted in another thread
. However, I wonder if this would be precise enough to create reliable alerts for OmniFocus location stuff. At what point would the balance be between false positives and never being close enough to get a precise location at all.