There are a whole raft of these folding hard top 4 seaters being launched, in Europe at least, this year..

VW Eos (Golf/Passat based)
Volvo C70
Ford Focus CC (can't remeber the concepts name)
Vauxhall (GM) Astra TwinTop
Mitsubishi Colt CC

and we already have a number of smaller cars..

Peugeot 206CC (2+2)/ 307CC (4 seats, sort of)
Renault Megane CC (4 seats, sort of)
Daihatsu Copen (2 str)
Nissan Micra CC (2+2)
Vauxhall Tigra (2 str)

Interestingly (or not!), both Audi and Mercedes are, currently, sticking with cloth tops on their four seaters - stating that the owners want it to be obvious that they're cabriolets....