I worked in non invasive BCIs for a couple of years (this was about 7 years ago). My current horizon estimation for a “put a helmet and gave usable brain computer interface” is never.

With implants, we are probably decades away.

What currently works best is monitoring the motor cortex with implants as those signals are relatively simple to decode (and from what I recall we start to be able to get pretty fine control). Anything tied to higher level thought is far away.

As for thought itself, I wonder how would we go about it (assuming we manage to decode it). It’s akin to making a voice controller interface, except you have to tell aloud everything you are thinking.