the new super car is not a supra, it will not wear the supra badge in any market, and will be a badged as a Lexus in the USA. It was testing with a V10 N/A motor in those spy shots, but the rumor is it has since been scaled back to a V8 (per Car and Driver, which had some great pictures of the car, and details of it's rear mounted raditators). Price point suggestions are in the 150k+ area. The car is intended to compete with the 911 GT3, Ferrari 360, Carrera GT, Ford GT, and the up-coming redesigned NSX.
There is no other MKV Supra in development, at least not one that will be out in 06 or 07. There was a 1 off concept car build with the V6 out of the camry, but the project was scraped in 02, because "Toyota's direction has changed". This is evident with the death of the MR2, and the Celica brands. Toyota has left the low volume sports market, and looks to pass it off to super high end cars, under the lexus flag.
PS All information I have is current as of the Tokoyo auto show this year.