FWIW, here's my own opinion of the Porsche situation.
I think they're "big company" now, which means they probably have internal politics and battling factions and all that. The 911 folks rule the roost because they bring in the most dough. They don't want to build 911's just because people want 911's, they want to keep them sort of a pinnacle. The higher ups in the company listen and agree due to ego as well as fear of change (and more realistically, fear that the change will hurt them).
The reality, however, is that finally building a coupe version of the Boxster will cause the true driving enthusiasts to buy them instead of the 911 because, well, mid engine is better. 911 purists will still buy the 911. Ultimately, though, the demand for better Cayman versions from the people buying them (assuming they do sell well) will cause them to build a "better" car than the 911 (something that will whip the shit out of the 911 at Nurburgring) and they will sell them by the boatload. That's my hope, anyway, because I want a Club Sport or GT3 version of the Cayman, but I won't be buying a 911 GT3.
Oh, and I really think you "only" hear about the Cayman S right now because that's all they are building at first. The base Cayman won't be available for several months after the release of the S. That said, I can't imagine the base car selling that well since I'm somehow doubting it'll be cheaper than a Boxster, but it's probably less desirable than one. Driving enthusiasts will want the S and people who just want a cool Porsche sportscar will opt for the Boxster if the Cayman is still more expensive.
The rumor is the first track ready Cayman beat the 997 by a decent amount at Nurburgring. Porsche then detuned the engine to put it a few seconds back. Wonder how long it is before you can get an aftermarket chip for the Cayman that gives you that power back?
--Donnie