The C90 will be built on the same Scalable Platform Architecture as the upcoming C80. As such, we can probably expect the new two-door to share the C80's gasoline and diesel drivetrain options. Given Volvo's affinity for plug-in hybrids, we wouldn't be surprised to see a battery pack show up eventually as well.
Unfortunately, none of this is written in stone. The C90 still hasn't made it into the Volvo model cycle plan, meaning the luxe two-door won't see the light of day until 2015 at the earliest. Still, the news underscores Volvo's intention to move upmarket and fight head to head with entrenched European luxury brands like Mercedes-Benz and BMW.