For mining the cards with 2 gb of ram are now obsolete, if you want to mine eth also the 4 gb cards because the eth dag is greater than 4gb so you need a card with at least 6 gb of ram, i believe that with the cards from 2 gb of ram you can still successfully mine aion
For those who already have 4gb they can other coins like ravencoin, ergo, TON, Alephium, these coins still brings some profits for small graphic cards it's not as if they won't do a thing just because ETH DAG is over 4gb already.