A good question, and in reality, my main point was that general trends will change. I can't predict how, but am almost certain, based on history, that they will. I doubt anyone but golf architects themselves will focus on earth moved (although there were at one time regulations in parts of Europe designating the maximum any site could cut or fill.....) but they may say we need to make it prettier, as that is a concern of average golfers and owners.
If forced, I suspect that the general trend of gca is still towards more sophistication, in that outside forces will require most new courses to serve many outside functions that compromise golf, if they are to be permitted at all. They do now - Real estate, flood control, environmental filters, and who knows what. I mean, what if the ball rollback comes to pass? Sure, it might be eliminating back tees, but that alone might change courses. (Be careful what you wish for) For that matter, I also believe the information age, and the next generation constant desire for instant information may change things, although maybe it would be more in the clubs, balls, carts and GPS side, not design.
In any event, many golf courses will "require" extensive retrofitting to meet the times, even if some think the designs are timeless. In watching the Beatles "8 Days a Week" documentary last night, it did occur to me that musicians, always focused on new material, really diss other musicians a lot less than golf architects (except, oddly, Lennon and McCartney right after they broke up) But golf architecture isn't pure art, it is business, providing product for business.
If you look back at the 50-60's, there was a lot of renovation work done in the name of modernization. Yes, some due to technical advances, but also some caused by architects finding flaws in the old way as part of promoting (their) new way, and hence, some major renovations. There is economic incentive to do so. If you look at Pete Dye, he unabashedly admits he looked for an alternate style to RTJ as a means to being known. Even the entire restoration movement had some economic incentive for those who chose to specialize in this new niche.
So, it may very well be that the design community, in combination with outside forces, will simply design for the then current needs (or if you are cynical, fashions) and in so doing, the collective mindset will simply be that 1990-2020 era designs may have been great "for their time" this is now, and then was then.
It just seems to happen that way.