Due to their power saving and low heat generating capabilities, it was evident that multiple core processors would feature in handsets sometime soon. Symbian and ARM partnership have taken on the initiative. They plan to come out with their technologies by 2010. The ARM SMP or symmetric multi-processor is now supported in the Symbian OS. Apparently the first dual core processor to feature in mobile devices will be the ARM Cortex A9 MPCore which was announced just recently.

The new multi-core technology will increase battery life, as each core will only be accessed, as it is needed.
Source