I think that brain interfaces for computers will be possible with a solid state miniatured and simplified and directional MRI machine that will look inside your brain and read out the patterns of certain neurons in your prefrontal cortex to make an input proposal that you can then acknowledge with a single finger input. There's been recent advances in the miniaturisation of fmri machines from the size of a small room to the this(pic) creepy head-sized apparatus, if they can have another magnitude of size reduction it could probably fit inside a head-band you could wear as a input-device.
I don't think you will get people to accept many implants unless they have medical benefits.
There simply isn't enough benefit in implanting a credit card chip into your hand compared to having it as a plastic rectangle.
I don't think there will ever be a normalisation of inserting stuff into your body, we have been using needles for medical stuff for centuries and people still try to avoid it as much as possible, I don't think you can get past evolutionary ingrained revulsion of having your skin pierced or having a foreign object stuck in your body. With some exceptions like the body-modification crowd.
As far as inserting chips in the brain go, if you take the neural-ink interface and instead of using it for a Bluetooth device you do something simpler like having a scientific calculator chip that is so low in energy consumption that it can run of harvested body-heat, you'll get people that have several orders of magnitude better maths-skils, but more importantly it will make maths effortless and fun, you have no idea how transformative this would be, and unlike most other application it will never get outmoded. It's a much smaller step than turning people into a hive-mind but consider that maths is the closest thing to a universal language we have and by enabling people to express ideas that way you'll get closer to the ideal of unified communication without having any risk of unleashing the borg