Here's a couple of experiences I've had buying new cars that were supply constrained.
When the MB SLK was first released a dozen or so years ago, supply was so constrained we had to wait 9 months from the time we placed our order until our car was delivered. Our dealer did not even try to charge a penny over MSRP. I learned that while MB could not force their dealers to not charge more than MSRP, if they learned one of their dealers did that, MB would cut that dealer's allocation for new cars. That apparently was a sufficient deterrent, because MB dealers could have charged way over MSRP for SLKs back then.
When we ordered a VW Jetta Sportwagen diesel (JSW TDI) in June 2008, these cars were supply constrained. We put down a $500 deposit for our car at MSRP. Several months later the dealer called to refund our deposit because they said it was going to take too long for them to get us a car. We objected, said we did not want our order canceled. We were assured that the order would not be canceled. We got our deposit back. It's been nearly two years, and that's the last we heard from that dealer. I have no doubt they sold their allocation of JSW TDIs at more than MSRP because most VW dealers - including every one of them we contacted - ended up doing that last year. We wanted a JSW TDI so we bought one from a different VW dealer in April 2009 at a premium over MSRP. We are quite happy with the car and don't regret the purchase, but I am not happy with VW dealers.
I have no idea what Nissan policy is about this. Are they like MB -- punish a dealer who charges more than MSRP? Or are they like VW -- hands off with their dealer pricing? The answer to that question may determine what we earlier adopters end up paying for our Leaf, because I think they will be supply constrained through 2011.