Bitcoin is a perfect example of this. It might stick around for a while mainly because so many people are already invested in it, but when it comes to features Ethereum runs circles around Bitcoin. On the other hand Ethereum will probably never be fully finished.
Miner centralization is a huge problem for Bitcoin. The fact that 11 entities control >90% of the hashrate, and that 2 control >50% of the hashrate is a huge issue for Bitcoin. The pressures we understand to be causing this are more significant in Ethereum at scale. Ethereum is not even at scale and already is doing worse than Bitcoin in terms of hashrate centralization.
Ethereum also has significant scalability problems. Bitcoin struggles to hit 4 transactions per second, and every transaction on Ethereum is substantially heavier per transaction than Bitcoin. That scripting system is not free, and already Ethereum is 20% as heavy as Bitcoin despite being 1/5th the age and having 1/10th the usage. And that's before the fancy apps like Augur have gained traction. Augur is significantly heavier than anything running today, and it's definitely not the heaviest app that people have gotten excited about.
And the development is almost fully centralized. The current state of Ethereum is that what Vitalik says is what will happen, and while there are people who could shut him down... they won't. At least not in the near future. Ethereum has already performed hardforks and has several more planned.
I agree that Bitcoin has taught us a lot of lessons that have paved the way for its obsolecense. But I don't think that Ethereum learned them, and I think that Ethereum will seem a lot less attractive after it has to deal with demand matching what is currently demanded from Bitcoin.
I would almost go as far as saying they are orthogonal products. Bitcoin, above all else, prioritizes decentralization. Ethereum prioritizes features and flexibility, at the cost of scalability and centralization.