I wouldn't call the Stang a sports car anymore. Here's my theory on the Mustang:
Ford is brilliant in one regard and that's how they handled the development of the Mustang. When it started out its life, it was there to challenge the 'Vette. Ford, though buyers didn't like it, made it more and more mainstream--to the point that it was almost crappy (those days are generally over, though).
The Mustang, which is mainstream now, competes with the Camaro, which is more preformance-oriented. Let me ask you, what is happening to the Camaro? It's getting cancelled. Cancelled. If Chevy did with the Camaro what Ford did with the Mustang, it wouldn't be cancelled. Although, unfortunately for Ford, what they did was compromise what the Mustang was all about -- fun, style, and power. But at least they're making money.