1. Governance
There is always some decisions that have to be made. There will be softforks and hardforks. There will be blockchain parameter adjustments. How these decision are made? Who can participate? The decision making process should be clearly defined to make sure there won't be situations like with Bitcoin right now – it can't make a decision how to scale, even when the blocks are already full. It's best to think blockchain as a DAO (decentralized/distributed autonomous organization) because it helps to keep in mind the organizational side of things. Not only technology is important, the system has to be also easy to use by humans. It doesn't matter how great the tech is if it's really difficult to actually get things done with a blockchain.
2. Scalability
If the blockchain wants to have lot of users, it must scale. Period. Preferably on-chain because that's what makes it truly peer-to-peer. EOS seems to be the most promising project for scalability.
3. Privacy
If a blockchain is used for currency transactions, as pretty much all of them are, it's important that users can somehow have privacy for their holdings and transactions. Steem is currently very weak in this regard, everything is very easy to see for everybody. If we want steem or SBD to become widely used currencies, there needs to be a privacy feature on the blockchain.
4. Free transactions
One of the greatest blockchain innovations of last year was free transactions implemented by Steem. Still very underrated feature and not recognized by the rest of the cryptosphere. But I predict that people will have to acknowledge that it's pretty damn great feature that can be used for many applications which are impossible with transaction fees.
5. Named accounts
Should be self-evident? Nobody wants to use public keys as addresses.
6. Price stable cryptocurrencies
Mainstream markets need something price stable for everyday use. Most people do not like when prices are too volatile. Also there is growing demand by cryptotraders who want an alternative for real fiat currencies that are very risky because governments can interfere with their transfers. Not a surprise that SBD has been lately valued for more than one dollar: the demand is huge.
7. Trusted/reliable smartcontracts
Wouldn't it be great if people could actually trust in smartcontracts? Reliability is linked to the language that is used for the code. Tauchain aims to be the king in this market by introducing a language that is very reliable, but it's still in the initial development stage. Tezos is also emphasizing this.
8. Off-chain computation markets
What if you want to make a smartcontract that needs more computing power than a blockchain itself can provide? It's possible to outsource it. Projects like Golem, iExec and Truebit are focusing on this.
Would you add something? Did I miss anything important? Please leave a reply and let me know.