A123 has also said it will make mass market battery packs for the Plug-in Hybrids PHEV in 2008 and is targeting a cost of about $10-12K with a 1 hour installation. Then your 04 or newer Prius can get 100+ mph on trips less than 60 miles. Even more on shorter trips.
I'm ready to convert my 05 Prius and would pay that price anytime they are ready. I will even give them Desert testing info since I'm in the Phoenix AZ area. I can also charge up from Renewable Energy on my grid tied solar system.
We already get 50+ mpg and I car pool with 3 of us so we get 150+ mpp, Mile Per Passenger. Soon I could get over 300+ MPP !