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.