Looking at the success of Ethereum in 2017, so many new ventures started their journey in order to compete Ethereum. Some took momentum as a matter of fact like Tron and Eos. Other names like Cardano and Zilliqa etc are also running in the race.
What do you think would Ethereum sustain this pressure and retain its leading spot?
How would the Proof of Stake, if implemented in time, work for Ethereum?
Would Ethereum solve their scalability issue?
Does Ethereum decentralization give it an edge over other centralized smart contract platforms?
yes it me possible to be the best investment in the future but there is always not predictable in the future so the cryptocurrency market is always about what is happening today and don't expect a lot in the future it will not give you the expectation in most of the time so my opinion is do what you want today.
No one can predicted the absolutely correct result of the crypto market but the case of ethereum is different buddy because they have already stated their plans through their road map when they talked about it last year. However, almost other smart contract provider platform mentioned by the OP have or will use the exact protocol planned by ethereum and for ethereum to have already gain the trust of project owners. Ethereum will always be the best smart contract provider.