It honestly wouldn't surprise me if at some point in the future, potty training becomes optional in society. I don't mean that in terms of being ABDL and hoping for it, but more just based on the trends in society.
I will personally admit, as I have many times before, that I was potty trained late. My folks wanted to have me trained around the age of 3, however between myself being a stubborn child and my Aspberger's, I wasn't fully day-trained until roughly the age of 4 1/2. I did wet the bed for a while after, but I can't remember how long for.
The way I see things, diaper manufacturers want to get as much money as they can for their products, which means doing anything they can to squeeze every last cent out of a consumer. Increasing the size and size range of diapers and their related products is a way they're going to make more money as society shifts moving forward.
As a good example, even though it's before my time, Huggies and Pampers (namely) only had sizes that ran up through size 5 in their products. It was either the late 80's or early 90's that the idea of a size 6 came to market. The reasoning behind it: some children potty train later than others, and need a larger size until they are ready to do so, or there are some children that are larger than average for their age and need a larger diaper. This came about more as a need the consumers had more than the company did.
Fast forward several years to when Pampers launched a size 7 diaper. From my understanding, the reasoning behind it was not for later potty trainers, but because they rationalized that children are different sizes, and need different sized diapers when they are nearing the potty training age. I think some consumers bought into the fact that it says it's a size up from size 6, when in reality it's meant to be another option if it works better on a child than a size 6 diaper. (I could be entirely wrong here, and apologize if I am.)
I believe that it's that sort of consumer rationale that leads to a shift in society where children are being potty trained later, if at all in some cases due to disability or other conditions. It's almost like a cycle: company releases new size, consumer misinterprets the reasoning behind it, potty training gets delayed, and then the company releases another new size or product (but this time to cash in on the demand). I can't even begin to tell you how many reviews I've read online of parents asking for bigger sizes or increased absorbency on products that they use with their older children (those older than the typical potty training age, if that's even a thing anymore), or their disabled children.
The way I look at it, I don't necessarily know if the continued prolonging of potty training would be a good or bad thing. I would say that potentially, if it gets to a point where potty training becomes optional, it could mean an increase in quality of store-bought adult or adolescent products, as well as an increased availability of them. With things the way they are these days, who knows what will happen.