This is a really big cop-out. I follow Ethereum pretty closely and I believe that the biggest threat to Ethereum's future is an attempt to move to proof-of-stake.
If you spend a bit of time in the ethereum community you'll find that everyone is very excited to reap the benefits for getting-in-early on ethereum, and they're very excited for the eventual switch to proof-of-stake so that they can collect money. Everyone who is invested in Ethereum is doing so in order to stake. This is terrible for the community, because who is ever going to get excited to invest in meme-powered internet money that they already missed the boat on?
What kind of testing is able to account for that kind of social effect? (Or maybe I'm just a stupid mathless Austrian.) Anyhow, that's just to talk about the social effects, and I think there are many technical problems with proof-of-stake beyond that... Let's not forget that there hasn't been a single successful PoS cryptosystem yet.
I also think that there are big problems looming within the EVM, and to give the article credit, that's mentioned and represented fairly in the article. (forward search for 'Bit-thereum' in OP)
I'm prepared to be wrong about Ethereum, even excited at the prospect. but if I was invested in a cryptocurrency it would be Bitcoin. I think that there are currency wars looming and I think Bitcoin stands to gain a lot from that. Bitcoin's big problems are overstated and will be solved in due time. It just needs to live past the death of Moore's law.