Make no mistake about it, the closest competitor fro ETH is NEO. Other potentials are EOS and ICON. But if I had to say could ETH be overtaken within a couple of years by anyone, then I would say NEO, for all the reasons already mentioned in this thread.
I also think that only NEO can compare with ETH. NEO and ETH have the same functions, and processing speed of ETH and NEO are the same. If I had a lot of money, then I would buy both of these coins and then hold ETH and NEO for about a year