I am not sure why you are still talking about concept cars. It was communicated that the production of the BMW Z4 ends this month. Normally, the production of the new model should start in a few months and be ready for year 2017. Do you think there is a special agreement between BWM and Toyota and Toyota will have to wait one more year till 2018 or even 2019?
And by the way, the new Supra will be in reality a Toyota as much as the GT86 is a Toyota. Expect the new Toyota logo to say now BMW, instead of saying Subaru: