Definitely Income. In order for it to be considered dividend, Ethereum (the company) will have to share their “profits”. Which they are not doing. They are allowing individual users to benefit from one of the abilities of the token. It’s not mandatory to stake the token. Therefore makes it an option for the holder or a source of income. Like when you choose to rent your house. It’s a source of income. Not the house paying you dividend. I think, but what do I know.
RE: Will Coinbase support Ethereum staking? If yes then Ethereum will easily become the most attractive asset to hold