Ethereum won't reach $5000 - 10000$ in 2018. I can see it reach probably $1k but Ethereum's base points stand within $720-$920.
I agree with your opinion. eth prices will be below $ 1000 if high also probably just at $ 1000 no higher. At present the number of investors in the market is high and the number of altcoin is high so the competition among the coin is quite high.
ethereum if s largely supported by investors and despite of high competition, it is not difficult foot this coin to maintain its present status. People trust this currency the most after bitcoin. It has remained at the top of altcoin world since ever which means there is something about this digital asset which helped it in defending its throne. It will definitely touch 5k dollars at least by the end of this year.