may have posted a while back about peeking beneath a friend's '06 Jetta diesel and being shocked at the length VW went to smooth the underbody with a patchwork of panels. i also heard that these panels are offered only on the diesel version - the less efficiency oriented gasoline model goes without.
today toyota released details of its 07 camry hybrid, and i noted with interest that it too features underbody aero tuning (panels, tire spats) which are not fitted to the non-hybrid versions:
"special attention was paid to the vehicle underbody with the use of wheel spats and underbelly pans resulting in a low coefficient of aerodynamic drag (Cd) of 0.27"
while two vehicles hardly constitute a "trend", it's interesting to wonder if manufacturers are beginning to see the light. the fact that the aero tweaks aren't offered across the model lineup makes me wonder if the day is coming when they may offer aerodynamic upgrades on the option sheet alongside floor mats and dvd navigation systems.
(decklid wings as options don't count; they're purely cosmetic on most cars; and where they do work as intended they increase downforce at the expense of increased drag.)
the camry's FE ratings are 43 city / 37 hwy (US)
of course, as with other hybrids, these figures will be either dramatically better or dramatically worse than the EPA figures, depending on how the car is driven. (hybrids seem to have even greater FE variability from the ratings than non-hybrids.)
compare prius and camry hybrid specs