It's just too slow to move it from main to video memory and back.
Also OpenCL works best when working on large pieces of data at once, with High frequency trading often you want to work on very small pieces, 50 bytes, and process them as fast as possible. Batching up the data and working on it in a SIMD type fashion just takes too long:(
(1) high technical sophistication, really hard to do (for each of the servers, network, algorithms, historical data, machine learning, etc)
(2) done behind closed doors (always interesting to get a peek)
(3) technically 'exploits' the financial system in a way that provides certain companies with immense profits
There are plenty of suppliers who offer stuff in the market, for example replacing one half of a dual CPU system with an FPGA and in general some variant of 'pick a fast interconnect and stick an FPGA at the end'
I can't see why this offers anything more to the discussion over a product announcement.