Go check the DAG Calculator:

https://investoon.com/tools/dag_size

You can estimate the difficulty, we're not near 4gb yet - and like an earlier poster said you should be more concerned with Ethereum switching to proof-of-stake (holding coins and staking them) rather than proof-of-work (which involves miners and GPUs processing transactions for a block reward).

If you can get any of these cards for RRP, you're laughing.