I assume that even if apps won't immediately be using both cores to their advantage, the Samsung system will, considering... well, it's natively made for that particular model.
There will probably be some sort of system or optimization that will separate tasks for the Android system (or parts of it) to use one core, and applications to use the other core (or possibly use both if the option is enabled).
Hell, at this point, for all we know, the system is completely optimized for this dual core process and controls every aspect so not only is the entire phone running at it's most efficiency with the cores in respect, but it's also possibly saving battery life.
Hard to know considering the specs were only released a while ago. It also doesn't help that there's only one other dual-core phone that is out right now to compare, and it was only released a few days ago, so developers still have to see how exactly the Android system handles the technology.