since the 2010 Prius was introduced in the first half of this year, will Toyota follow suite with the 2011? Or will the 2011 model be introduced in the more typical time frame of Sept.-Nov. of 2010, giving the 2010 model an extra-long year?
I kinda wondered why we didn't get them as 2009.5. I remember when Nissan released their Hardbody trucks (significant redesign) in 1986 as a 1986.5 model year.
.5 years are rare... there was a 1999.5 Infiniti vehicle... I forget which but I think it was the I30. As for the length, it depends. Toyota has kept the one year cycle for the Corolla (so releasing them in Feb-Apr of each year). Others like the Camry have been all over the place.
It's pretty common with a new model or redesign, for manufacturers to introduce them earlier than the normal September/October time frame, and then release the next model year 1+ years later during the normal MY release cycle (likely September/October 2010 in the case of the new Prius). While there is some flexibility in MY designations, at least in the U.S., there are some restrictions, so to release a MY '11 in September 2009, for example, isn't allowed.
In my opinion its safe to say the 2011 will come out like a normal model year, around September/October 2010... But who knows for sure.