Although [former Jordan, Stewart and Jaguar technical director Gary] Anderson [...] reckons the full effect of the change will only be seen when testing starts, he suspects that the greater reliance on aerodynamic grip will hamper passing attempts.Basically his argument is that since the front tire size is being reduced, mechanical contact-patch traction will be diminished; and the natural development of aerodynamics will increase aerodynamic grip. Aerodynamic grip will fall off as the cars close with those they are pursuing, which means the cars will be correspondingly more sensitive when following closely, which is not what you want to encourage passing.
I have said before my concern was that the 2010 rules did not promote passing, and with refueling illegal now there is less opportunity for "strategy" to play a part in who finishes first. Reducing the cars' capability to make passes even further won't help.
2010 could be a dry year.