Though coinbase announced that they would be supporting ERC20 token in the coming months (https://blog.coinbase.com/adding-erc20-support-to-coinbase-fe9cba6782b), I don't see them adding ERC20 of EOS since the mainnet is slated for June, Coinbase will wait till after July before considering EOS addition.

So, adding EOS to Coinbase is just a matter of when