Our evolutionary gift isn't intelligence, it's adaptability. We are by far the most adaptable species on the planet. The big brain is just one of the mechanisms we use to achieve it. That is never going to stop being useful.

I don't think two way implants are ever going to be a "thing" the way they're portrayed in fiction. Every brain is so different that it would have to be wired completely differently in each case. On the other hand, one way implants that allow a computer to "read" your mind are totally feasible and will definitely happen in our lifetimes. I doubt the resolution will get good enough that they'll be super useful for regular people, but they may help disabled people, and they'll create a much shorter feedback loop between man and machine that will be useful for specific tasks.