I think that the main token which should Eth holders a bit worried is EOS. if they do what they say they can then it might just destroy the dominance which Ethereum has in the smart contract platform.
I don't think EOS has that capability simply because to get to what they're proposing they've sacrificed a lot of decentralized consensus for centralised control- in the same way that Ripple is never going to seriously challenge Bitcoin. They'll co-exist for a time and one will be more dominant than the other, but it's not going to be a binary market solution of winner/loser.
