Don't get me wrong I'm sure there will be advances. But this current tech is based off reading nerve data meant to be movement data - the user needs to mentally trace each letter.
So I don't see this form of the tech at least being able to compete with qwerty let alone stenography.
Actually to that point, stenography would allow people to input data (it must be language specific and error tolerant but most BCI is as well) at ~5x the average typing speed on qwerty but that hasn't proliferated.
EDIT: On second thought I could see it matching physical movement, maybe _slightly_ outperforming it by a few % by skipping a few physical limitations. I think this should be essentially identical to any other physical motion based communication.