I doubt T bar will ever go away in commercial buildings. It is a cheap and effective way to deal with office space built in steel truss construction and easy to change when the floor plan changes. I agree it has fallen out of favor in residential.
There was a lot of abuse of that space by IT techs, I was guilty of that myself. A lot of that got fixed when they bought us a taller ladder so we could string our CAT5 and coax through the steel trusses and not right on the grid
I still would bet there are non rated data cables and even orange extension cords running through most office ceilings.
