In theory, a miner could try to manipulate the hash of the future block to change the outcome. It is much more difficult with Bitcoin, where valid blocks are more rare and produce a high income, but with Ethereum blocks are so frequent that it might be possible to collude with the mining pools is done on a large scale.

Additionally, how does this deal with Proof-of-Stake algorithms? Ethereum is heading there, and as far as I am aware the blocks would no longer publish hashes.