... ethash uses memory which is something a fucking asic DOESNT HAVE,
so unless theres an asic that has memory, but at that point it would NO LONGER BE AN ASIC as you would be able to run anything on it since its soooooooo danm close to a PC
ASIC is ASIC and memory is memory. ASICs use memory if required(fuck why not?), more than that ASICs often based around RISC CPUs(some low end ARM 9 for all the surrounding stuff may add a few bucks but solve lots of issues. I'd guess that if you build an ASIC miner you won't put ARM core for each algo solver though...)
And as for the GPUs usability just a thought for you: when Google were teaching(neural network) their Google Brain they have acquired few thousand GPUs for that purpose.