Good to see RocksDB and HF20 getting close to completion. I notice you haven't left any dates - kudos, that's the sign of a maturing organization. Only leave release dates when you're absolutely certain you'll hit them. Of course, keep us updated while development is ongoing - exactly like this.
Also, I would suggest branding the RocksDB release 0.19.5 to separate it from current 0.19.4 RC doing the rounds. Some witnesses are using it on production nodes, no less, so there's potential for confusion. RocksDB is a pretty dramatic shift for the Steem blockchain (and blockchains in general), and needs its own point version, at least.
RocksDB is technically only for account history. (It won’t have an impact on witness nodes.)
Separating it out from the current “master” branch could introduce new risk into the code they have already been testing for weeks. It may be more trouble than it’s worth.
I also don’t know what real benefit it will provide since it sounds like all the node operators who are running account history will probably want to pick it up as soon as it is available.
Also FYI, some witnesses (myself included) have been running the RocksDB plug-in on some test nodes for a while now too.
Oh, I just meant purely a naming/branding change for the final release. Anyway, not an issue either way.