I dont think that its a question of "if" toyota will bring it back but when. Every Japanese automaker has a signature pure sports car out, from the s2000 to the STI. Im sure that there is a car in the works @ toyota. But the question now is will it be a supra mk5 or another totally different sports car.
As far as the engine I think it will be a N/A V8 that has some scrap parts from its formula1 and cart cars. Oh well lets just wait and see...