Actually, the segment has been relatively stable. It has never been a huge segment and it will never be, but it is a stable segment. Economic downturn or not, the clientele for V12s are not impacted as much as the middle and upper middle class. The middle and upper middle class do not buy V12s. The more over the top the flagship is, the better it will fulfill its mission of bringing prestige and recognition to the brand. Of course, grabbing a few big spenders along the way doesn't hurt. But, selling itself is secondary to helping sell the Bi-turbo V6 or V8 Omegas, not to mention CTS, XTS, SRX and ATS cars. If you want middle class business, lower the entry price of ATS or simply show them the way to the Buick dealership.
In fact, a 14-liter V16 made using the equivalent of two pushrod LS7 V8s mated with a new block making about 1010hp / 940 lb-ft will be even better from a prestige standpoint. The problem of course is that there is no transmission for it and rear drive is no longer viable for putting all that power down.
I don't know, I just find it ludicrous that the bigger the engine the more prestigious Mr. 70-year-old-CEO finds his car.
Ironically, the only individual I've personally known that had a V12 car was a 50-something yr old tech company CEO/chairman of the board--a BMW 750iL. Sweet car, rode in it a few times back in '02. The company's 30yr old founder and CTO drove an Audi TT roadster. The other 2 tech company CEOs (40-somethings) that I've known drove Priuses.
Anyway, I'd be really surprised if GM developed an exclusive DOHC V8 or V12 for a Cadillac flagship...if it can't be shared with the trucks, it isn't happening seems to be the MO at GM as far as larger engines, unfortunately.