Interesting comparison, but I don't know if I fully agree with you. If the Supra fails, only the faithful fans and the the auto enthusiast will notice. 99.99% of American drivers will never even consider the car in the first place, and probably don't even know it exists. The auto buying market as a whole doesn't car about sports cars. Toyota will continue to crank out millions of Camrys, Highlanders, Rav-4's, and Corollas. I'd be willing to bet the production of the Camry in a single day will probably be more than the best-case production run numbers for six months of the Supra. It's a hyper-niche automobile. Toyota is the #2 largest auto producer in the world and the whole reason they partnered with BMW was to reduce development costs, but also financial risk if sales don't meet expectations. If the Supra fails it will be in the auto press for a couple days and then simply become an entry in a Wikipedia page. The company will press on with barely a hick-up. A third party builds the thing in Austria, so Toyota employees won't even be effected if production ends.
The Cimarron was a terrible car based on a shockingly horrible platform even by miserable GM standards of the 80's. That platform wasn't even worthy of the Chevy badge it wore, let alone the Buick, Oldsmobile, or Cadillac. Everything about the car was bad; engine, unibody platform, interior quality, workmanship, the fact it looked a lot like the Cavalier, the whole bit.
The new Supra is a different story. Mechanically, it should be fantastic. The BMW B58 inline is a fantastic power plant. I've driven it first hand in a couple different applications and have never been disappointed by the way it delivers power or it's output. The CLAR platform used in many new BMW models has received rave reviews. Interestingly, there version of the platform used by Toyota is unique to the car since the Z4 will only by sold as a convertible. Car and Driver actually liked the dynamics new Z4 (the foundation for the Supra) better than the 718 Boxter, which is very high praise for the engine, suspension, and overall platform. Toyota commented on tuning the Supra to be even more driver focused than the GT-like Z4, so any driver should be in for a real treat.
The Cimarron was a cheap, badge engineered, turd which totally missed the traditional Caddy buyer's ideal (too small) and didn't live up to what was left of Caddy's reputation at the time. It was terrible regardless of what brand logo GM slapped on the hood and sales were tanking across all the brands. The Supra, if taken in isolation, should be a great car. Toyota's only real sin seems to be using the Supra badge. Had they called it something unique like they did with the F86 (why is that car not a Celica?), I bet the reception would have been totally different. Styling is very Japanese, which these days doesn't seem to resonate well with US customers regardless of whether it's Honda, Acura, Toyota, Nissan, Lexus, etc.