As long as there's trucks there will be V8s, imo.
That doesn't mean they'll keep stuffing them into cars, though. From a business and logical standpoint...why do that, when a Turbo'd V6 will give you just as much power and torque + better fuel economy?
Given the recent advancements in powertrain (direct injection coupled with turbos, VVT, etc) there's no performanc compromises by using a V6 instead...I think the only people who will mourn the potential loss of the V8 will be those who are emotionally attached to those two extra cylinders.