I'm more sold on this becoming contact lenses and hearing aid like objects than implants directly into the brain. Silicon photonics is already making this stuff semi possible.
I was thinking in tangent with what @Thomas Larmore suggests here Perhaps they could be listening to all the club’s latest jams via an implant in their heads and all moving in sync to the music this way. It could be partly based on actual news and have a true element about it. Edit: or an electronic earpiece or something .
Still don't see it, especially by 2040. People have been predicting this stuff at least since the cyberpunk days of the 80's, and that was almost forty years ago. The things people could theoretically have implanted today, we don't because most of it would be insane, not to mention cost-prohibitive to all but a minuscule minority. I just don't think people will be willing to have brain surgery to eliminate carrying phones. I would much rather have a screen in front of me anyway.