But when will have programming languages that can accommodate them? Haskell gives some hope, and Go, but we're no where near where we need to be for mainstream developers to take advantage of so many cores.
There is already a great deal of language support, and having boards like this will certainly help popularize the parallel programming skill-set. Since it looks like there is an integrated FPGA, I'd like to see Dynamic Method Migration[1] make some progress too.
Given the libraries, mainstream developers will probably have no problem taking advantage of this class of hardware, using whatever language they might deem appropriate. Of course when I see this board, I think more about nonlinear PDE than web apps... so, how are you defining mainstream?
Any ideas?