There are different types of SRAM. High-performance SRAM has 6 transistors, 6T. Intel may use 8T Intel Labs at ISSCC 2012 or even 10T for low power? (see real world tech NTV). It would seem that SRAM should be about six times less dense than DRAM, depending on the number of transistors in SRAM, and the size of the capacitor in DRAM.
There is a Micron slide in Micro 48 Keynote III that says SRAM does not scale on manufacturing process as well as DRAM. Instead of 6:1, or 0.67Gbit SRAM at the same die size as 4Gbit DRAM, it might be 40:1, implying 100Mbit in equal area? Another source says 100:1 might be appropriate.
Eye-balling the Intel Broadwell 10-core (LCC) die, the L3 cache is 50mm2, listed as 25MB. It includes tags and ECC on both data and tags? There could be 240Mb or more in the 25MB L3? Then 1G could fit in a 250mm2 die, plus area for the signals going off-die.
There is a lot of depth in this blog post.