Anything is possible, but this would be rather surprising. Toyota are pretty good at keeping new models secret. I'm even suspicious the "spy photos" are allowed to happen to ramp up excitement.

Anyway, a new model usually is based on something already here, with lots of tweeks and improvements. A totally new concept is not impossible, just unlikely. Perhaps looking at the concept car shown in Germany last winter would give better hints.

There was a sports car concept shown at a show last year - a possible replacement for the Supra. I don't recall if it was rear engined, but it was 400 HP and a hybrid.

Pearl is a
2007 Driftwood Pearl Prius
Package "B" (everything but leather, nav, and rear camera)