I am also in the process of getting a Z, but I would do more research before pulling the trigger on a 2011 base model with sports package for 40k. With that much money, you can get a Nismo or Touring with sp.
I asked myself the same question, whether or not I should wait for the new model. There are only going to be minor changes and if you don't track or mod, then it really shouldn't matter. Either '11 or '12, Z is going to be a Z and they are always gonna come out with newer models.
This forum is really great and I suggest you read Ak370z's guide to getting the best deal (invoice pricing and very low interest rate). Good luck to you!