My concerns regarding Ethereum are two fold; J.P. Morgan support may lead to them being a tool of the central bankers. Secondly their blockchain does not appear to be immutable . In other words, verified transactions could be rolled back.
Last time there was a split into Ethereum and Ethereum Classic, Coinbase, I believe had to kick in funds to make everyone whole, when the blockchain split into two separate currencies.
Keep your eyes open.
Yeah It's worth of good concern that you raised over here, That's the result of Split of Hard fork which resulted ETC (Ethereum Classic). there is also chances in Bitcoin to be undergoing SEGWIT ( BIP 148 ) Hard & Soft fork. the outcome is unknown yet due to much speculations which can be known after the event to be taken place.