The iPhone 4S is rumored to include the same amount of RAM found in the ageing iPhone 4, just 512MB. The Infinity Blade developer was quoted last week:
I'm still shocked that, with the iPhone 4S, I'm literally running around with a 1080p video camera in my pocket, with an eight megapixel camera, 64GB of hard drive space and an A5 chip with 512MB of memory. This is a really powerful computer, right?
They would be more inclined to know, as they demoed their game on the iPhone 4S during last week's keynote. AppVV is now also confirming the rumor of 512MB on the iPhone 4S. But, I'm sure we'll find out soon enough.