I just don't think that we have enough information to really make a judgement on how many sales Nissan will get from the IDx. We have no idea what segment its going to be competing in really. We don't know how many units its competitors sell.
depends on what you want to view as competitors. A popular one has been the FRS, but you could also consider (being a budget coupe and all) the Forte Koup or Civic Coupe. All depends on how they decide to dress the IDx...
I think that there will be one model that is more casual but that one will come with an automatic transmission I would guess. A higher end model could get a manual transmission but it would also get an automatic transmission as an option.
It will be interesting if Nissan tells us what they are expecting to sell with the IDX. Knowing how Nissan sees this model playing to the public will help us figure out how much it will sell, who is going to buy it, and what its main competitors are.