I think its just becoming more and more passe to have numeric designations for U.S. cars -- especially the way Lotus traditionally does it. The U.S. market would freak out about "so many different models" which are really just small tweaks to the same thing.
Just take a look at the user interface of sites like kbb.com and edmunds.com, they all assume a unique "model" name that will continue through the life of the car, and they have "sub-models" from ther. (Well, I guess 111R could be the "sub-model", but whatever)
Steve