The 2012 Mobile World Congress was the unofficial coming out for quad-core processors. Since then Samsung, HTC, and LG have all released smartphones with four-core processors. Earlier this month DigiTimes published a report saying Apple is working on a quad-core processor based on Samsung's Exynos 4 architecture for the iPhone 5. Seeing as how the iPad has a dual-core A5X processor, that would make the iPhone the most powerful mobile device available from Apple.
Quad-Core A6 Processor