True but the probability of GPU reaching L1 cache parity is much higher in the short term.  I would expect it within 1 generation (8000 series) but if not there it will certainly be there in the next-next generation.

So realistically you are talking about a 2-3 window before GPU have cache parity with CPU.  Using an algorithm which relies on that inequality is "futile" over even the short term.

Honestly I don't see the value in trying to limit hardware.  At this point GPU mining (which we don't even know exists) is still more valuable on Bitcoin.  So if someone was convinced Litecoin will take over the world it would still be cheaper to mine BTC and use that to buy LTC.  If miner i just interested in fiat profits well all that matters is which coin generates higher return on a given piece of hardware (or even more abstract a given amount of capital).