2009/10 should be the last year of production.
The SC430 has not changed besides small exterior changes. The engine and technology basically stayed the same. Instead of a model change-over, it is being discontinued.
As of now, the new IS-Convertible Coupe is coming out and is much more affordable to the general public. For now, the need for the SC430 is scarce and there isn't much demand for it anymore. It's just been overdone for too long.
Think of it like the old LX470, it discontinued for awhile and now they came back with a LX560.