Time to chime in here
Cockpit views are immersive, yes. I also grew up in the Test Drive/early Need For Speed era with cockpit views. They're nice and pretty, and they make me go "ooh so THIS is what it feels like to sit in a GT car", but at the end of the day they amount to screen clutter. A RL car is not limited by a small amount of screen real estate.
Imagine driving your RL car with the door windows painted black. You can only see through the windscreen, no peripheral vision. Sounds like fun eh?

Now try doing it at 150mph with a bunch of other cars all around you. Yeah right. You'll be dead by turn 4. No, most people do not have TrackIR (or are able to make effective use of the "look left/right" feature of the GT4 bumper cam). So to answer all those who ask why the bumper cam became de facto, the answer is simple: screen real estate. To offset the narrow view available to the gamer, they have to maximize their use of said narrow view (similar concepts to those used in software user interface design).
As for generic cockpits, I doubt we'll see them for two reasons: 1) KY won't like the idea, and 2) neither will many many fans. For better or worse, racing games now rely heavily upon visual realism and detail in addition to all the rest. If my RL RX-8 exterior looked the same as the Mazda6 in GT, I wouldn't be very impressed. Likewise, if the RX-8 cockpit looks the same as the Mazda6 cockpit, I'm just gonna turn it off (well I would anyway, but you get the idea...). The bar has been raised too high to move backwards in this regard.
I'm playing GTR also, and as someone else said they only had to model a handful of cars. The on-screen steering wheel is a pain since I have my DFP setup for 540 degrees for GTR and the on-screen wheel turns less than the real one, so it's off-putting. The info displays on the dash are too small to be useful during a race (if it was rendered actual size, maybe, but that would require a big TV/monitor). Plus you have no legs. Okay, I know we're modeling the cockpit not the driver, but c'mon, if you're gonna give me the ability to look down at the pedal well, show me my legs! That's just creepy
Anyway, I think a happy compromise would be the ever-elusive hood cam. Like the roof cam, but not on the frikkin' roof!

And with the same level of "feel" the bumper cam gives WRT weight transfer etc. because that roof thing feels like I'm driving a solid concrete slab. Maybe they could even offset the cam to the driver's side of the car, and perhaps even model the windscreen frame (that would be easy to model for each car, not much involved except shape) along with the hood of the car. Then maybe simulate the real dials. That should be reasonable.
Oh, and to whoever said they can model 50 cars a day, apparently it took something like 3 weeks to completely model a single car for GT4 (visuals, sounds, etc.) and that doesn't include the dash/dials. 👍