Could be all the rumors about Metallica are bogus and Stern is going to pull a surprise theme like this in April. Wouldn't be the first time they did a little mis-guidance on everyone regarding a theme.
The question is, how well would a game about the iconic American muscle car sell outside of the US? Would the European operators be interested in the theme and order? If not, the theme is unlikely to happen and Stern will continue on with the Sci Fi, Music, Super Hero line up that is doing so well for them in the market right now.