It is very hard to predict the future of ethereum. Humans are developing with tech so fast, it can become scary sometimes. My friend told me that ethereum is a crypto bubble. The reason for that? Better things come out. There are so many projects and crypto currencys, that no one can know which will lead us. Bitcoin is very popular but very slow, ethereum could have in future problems with tech or even with the smart contract implementation in real life ( legacy, rules etc). You can discuss about those topic for hours, but in the end you have to choose your own opinion. When humans stick to ethereum and stay loyal to it and dont want something new or even better than eth( which in my opinion never will happen) then the future is really good. Else a new currency will lead with much more scalabilty, privacy, etc…