To be honest, depending on what you mean by "automotive photography", I would consider a few things. If you're talking more of something like car profile pics (car portraits so-to-speak), I'd personally just go for a decent lighting setup - a strobe, softbox, stand, power source, pocket wizards, etc...
I know you're asking about a lens, but personally I think your arsenal is good for profile shots. If you're trying to get racing shots, I'd sell the 200 f4, get a 200 f2.8 mark II, OR keep it and save more for a supertele. That's just me though. To each their own. Photography is an art, it just all depends on your style, subjects, and what you're going for.