I'm not not aware of Tesla saying that they are considering a super-coupe on the Model S platform. But Tesla has said that they plan to do a next gen Roadster, and that it will shred.
Tesla Roadster To Return In 2018: Report | Reviews | Prices | Australian specifications
But the version from this article is basically just adding more power to the Model S chassis in a coupe layout, which could take the Model S P85 up a notch, but does the market really want that? The Model S Perf is already more oomph than almost any buyer in that category wants or needs, and represents the performance version. The car isn't designed to be a killer, but rather a large luxury car, and it does that very well, with a perf version available for those wanting to be able to beat a 911 in a large luxury sedan.
Is there enough of a market to do a Tesla version of an M6 super-coupe? As I wrote above, I think they pretty much already have that. It is the Model S Perf. They also have the 85 kWh standard for those not needing to accelerate fast enough to make your passenger spill their coffee and gasp. So I think they've covered that market, and I think that THEY think they've covered it.
Should they make a Model S convertible? I don't think so. In 2012 BMW sold 7,880 6-series convertibles. If you combine that with the 5-series (which doesn't have a convertible), that is 2.2% of sales for convertibles as a percentage of converible+sedan+coupes. If you combine the 6- and 7-series, convertibles are 9.6% of sales. The 3-series is made up of 5.9% convertibles. (2012 US sales)
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So I don't see much value in adding a luxury convertible to the Model S line (with "value" defined as incremental, profitable sales).
There may be a Gen 3 convertible, or the next gen Roadster may be a start-from-scratch effort to seriously compete with supercars. Or both. But I doubt that you can compete with the big boys with a Tesla electric version of an M3 convertible, with Model S styling and language adapted to the purpose. They may do that, but I think that isn't really the halo car that the next gen Roadster will be. At least I hope they aren't satisfied with a Model S shrunk down and made into a convertible. The competition definitely won't stop there. And GeorgeB doesn't seem to want to stop there. And we all know how Elon feels about this. And the Furai within Franz wants to go there. I mean, the Model S pays the bills, and we'll see about Gen 3 styling. But I'm sure that in their spare time the design team is often drawing up Roadster supercar designs.
Tesla Roadster To Return In 2018: Report | Reviews | Prices | Australian specifications