assuming there is a next-generation Baja, that is...
This is using power moonroof technology. If the bed cover were made up of 3-4 pieces of 1-way visible or deep-tinted hard plastic, it could "nested" up against the rear window much like that shown in this '05 Pontiac's sectioned moonroof, with the nesting perhaps a bit more vertical and closer to the rear window. If it were 1-way visible/deep-tinted plastic, the driver could see through the nested panels when looking rearward.
As to costs? Probably in the range of the moonroof pictured here, maybe a little more, since it would be a bit larger. My guess is that this Pontiac moonroof is priced reasonably, otherwise GM wouldn't offer it on this price-conscious mainstream brand. Frankly I'd trade the current standard moonroof for this moonroof-like bed cover solution, if costs were a real issue.