Right now, I'm most interested in seeing RethinkDB see more traction... it seems to have most of the features I look for, and I, for one don't mind more programmatic queries, and the management interface is really second to none at this point... MS-SQL, I'd probably consider a close second.
I'm going to have to disagree. The German HyPer DBMS has a lot more interesting ideas. Cockroach is just distributed MVCC from the 1980s on top of a key/value store.
MemSQL also has a new LLVM architecture written by the HipHop VM inventor that they poached from Facebook.
Yeah. Not so much. I can't think of anything that used the 2 phase transactions over independent consensus groups (aka spanner) pattern from the 80's. Likewise there was nothing like Yabandeh transactions in 1980 because no one actually understood serializable snapshot isolation then (but several projects mistakenly thought they had, which was Yabandeh et all's entire motivation).
HyPer is neat work, but that it is interesting does not mean CockroachDB is not also.
And according to HyPer home page, HyPer doesn't look distributed, which is another big difference.