By charging travelers to check bags, the airlines have created a situation that slows the boarding process down, at least for those in the back of the plane. On several recent flights, the gate personnel repeatedly emphasized that the plane was full and that all carry on luggage would have to be checked as soon as the overhead bins were filled to capacity as passengers boarded. The woman next to me commented that she had paid to check her bag on her outbound flight, but realized for her return flight that she might as well wait until it was her time to board because the airlines would gate check her bag for free if there was no room for her to carry it on. And turns out, that is exactly what happened.
The airlines make way too much money from charging for bags to be checked so I don't see that practice changing. What I do see possibly happening is airlines prohibiting a passenger from taking a carry on item that must go in the overhead bins without the payment of an additional fee. Some carriers are already strict about only allowing a traveler to take just one item without paying extra for a separate personal item.
As a committed carry on only person, I am going to change my practice (when I'm not paying extra to get seated on the plane earlier) and try to take a bag that can be squished enough to fit under the seat in front of me so I can avoid the gate check risk entirely. Unfortunately, that means no roller bag.