If a convertible was in the pipeline the whole time (which is likely), then they would have engineered that into the car from close to the start. it may not have been released as a convertible first but I doubt it's an after-thought for Toyota to release one.
Subaru BRZ And Toyota GT 86 Production Gets Underway [W/Video] Finally. It's the moment we've all been waiting for ever since Toyota and Subaru jointly announced their compact rear-wheel-drive sports car: production is now underway. With an official ceremony at Subaru's Gunma Main Plant, attended by Toyota president Akio Toyoda, Subaru pushed the Big Red Button (quite literally, in case you were wondering) that sent BRZ and Toyota GT 86 coupes down the assembly line. And the event was captured in both still images and video for our viewing pleasure. http://ca.autoblog.com/2012/03/16/subaru-brz-and-toyota-gt-86-production-gets-underway-w-video/
Got to see the BRZ and the FRS at the car show last weekend. They were both on raised(ish) plastforms so they were hard to get a real feel for. They are so close to identical it's amazing. I reaaaaaally wanted to sit in one, but you couldn't. Both of the seats (BRZ and FRS) were fully extended back, which left not even a cm of rear passenger space. I want to know how much room passengers would really have, when a gigantic person is not driving it. They said the FRS is coming in at under 30k Canadian, and the BRZ around 32.
Here's one w/ a IS-F engine. http://www.autoblog.com/2012/03/30/well-that-didnt-take-long-v8-powered-toyota-gt-86-drift-car-un/#continued
+1 for "well that didn't take long" in the url. But for real, in that size of a car, I cant imagine the weight distribution to be good with a huge v8 in the front. I'm thinking we go back to aspiration and throw a tt 6cyl under the hood and push out the same power for much less weight.