dual-core is irrelevant when your OS is not optimized for it
Gingerbread is.. which is what will ship on it.
The new Android 2.3 Gingerbread has new file system called ext 4 under the hood. This file is very common in Linux distributions. The ext4 file is making its way to the Android mobile OS after it has been running in Googles massive data centers.
Starting from the new Google Nexus S, ext4 is attach to the system. This file is used to improve support and performance of the device running the OS. It helps to deal with large files and large storage, it is not a problem we experience in mobile though but it is surely an advantage.
Earlier the Android uses YAFFS file system to handle flash storage, but unfortunately it could only deal with single core device processor, so even if later it powered the dual core processor Android, it would not get high performance boost.
But with the ext4 file system, a single core Android device will get performance boost and even higher when it works with dual core processor. However, according to Theodore Tso as the ext4 developer that who is also a Google employee, this ext4 system file will increase the chance of data loss.
But dont worry, when it finally goes to the market this issue surely has been fixed as vendors do extensive testing before shipping a product. For Android advanced user, you can grab custom ROMs for various phones that enable ext4 at XDA Developers forums.