Regarding the original topic, the literature carts, I doubt the organization will do away with them. I don't think they care if the people manning them are looking at their cellphone or going to Starbucks, anymore than they care if the average JW only knocks on three doors, talks to no one and then goes for donuts every Saturday. It's all about appearances, hours reported and keeping the flock busy. The average JW makes a pretence of preaching, and the Watchtower doesn't care because they no longer make money from it.
The literature carts give the illusion that they are progressing and moving ahead, and that's enough to keep people contributing, at least for now. The slackers manning the carts probably feel slightly guilty for getting away with easy hours, and guilty people are easier to manipulate.