I think the message will change a bit over time, in the way that it already has over the past century. Remember that, in the earliest days, the WTS set specific times for the end of the current system of things. 1914/5, 1920, 1925, for example. They learned some lessons and in 1975 tried to mix in some uncertainty, which did not work as well as they had hoped. When they initially eased off the (revised) 1914 teaching, it was by very quietly dropping the "this generation" language in the magazines.
They have held on to the "the end is near, it is very near" talk, and that might be the next thing to change. Already, it will not be long for Lett's "last day of the last days" message to age poorly. At some point, the message will become more like "who knows?" They will continue to point to world events, but I think they will leave it to the rank and file to sort it out themselves, and hope that most decide to stay in.
As more time passes, the old message becomes problematic. It is now almost 50 years since 1975, which means it is more than 50 years since they started the talk about 1975. If you had told any of those witnesses back then "the end will not arrive for another 50 years," how many of them would have sold their homes? Refused to have children? Refused to marry? Refused to prepare for retirement? Any JW who does the math will run into a very rigid wall made of cognitive dissonance.