Here is what the Collector Guide has in it for this year.
Cars Toon
Rescue Squad Mater
Burnt Lightning Mcqueen
Dr. Mater
Nurse Mia
Nurse Tia
You can find it here.
http://carstoysblog.com/upcoming-cars-checklist/">
http://carstoysblog.com/upcoming-cars-checklist/
Also, the SDCC exclusive this year is a special version of Rescue Squad and Dalmation Mia and Tia that will be different from the retail version. You can see it here.
http://carstoysblog.com/2009/04/01/sdcc-2009-exclusive-rescue-squad-mater/
Next on the list should be Mater the Greater. Prototypes have shown up of these as well.