Except for niches, one is not going to unseat SQL as the primary de-facto standard relational query language unless the replacement is significantly better, not just slightly. Unless a fad storm kicks in, being slightly better is rarely enough to unseat an established standard.

As far as SQL competitor candidates, my personal favorite is SMEQL. It's more composable and uses tables for many operations instead of dedicated commands and syntax, making it more uniform where a handful of idioms do all the work instead of lots of specialized stuff for each task, like what SQL does.