I think it is unlikely that ETH becomes the next Bitcoin for two major reasons. First, they serve slightly different purposes. Bitcoin functions better as a currency and Ethereum functions better as a smart contract. They can be mixed in other capacities but that their major strength. Second, Bitcoin has been around since the beginning making it much more stable as the primary store of value. ETH, meanwhile, is much more likely to be dethroned by a smart contract 2.0 technology.
Of course, anything can happen, so don't just take my word for it!