What diseconomies of scale do you mean? If you mean that demand is low right now and so there is no economy of scale yet, that's hardly evidence against a gradual market takeover. That's what investors and early adopters are for, see: SSDs. If you really do mean diseconomy of scale, where unit price will rise with the number of units produced, what would produce such an effect in the SRAM market? Chip fab is almost always in the opposite regime, what's so unique about SRAM?

Also, I looked up RLDRAM [1] and it looks like their "low" latencies are still 10ns, which is good for DRAM but abysmal in comparison to SRAM.

[1] http://www.micron.com/products/dram/rldram-memory/1_15Gb#/