i would imagine that there is no motivation to do a V12 now, considering the V8 has been doing well. the 'upgrade' or 'improvement' will be the 7 speed AT for 2007.
a V12 QP will be disaterous to the 612 sales, don't you think? granted a v12 QP will carry a premium like all other V12 MB or BMW's over their V8 counterparts. I love to see one, but if I am paying close to $160k+ i might as well go for an Aston Martin Rapide when it comes out.
a V12 QP is not going to give a big boost in sales volume the company is looking for.