I can certainly foresee a shift towards 9 hole courses for the masses, due to time commitments in life, short attention spans of millennials, and difficulty of standard courses. With the craze of TopGolf, which packages golf in with more standard casual pursuits of mixed company, food, drinking and having a good time I can see some 9 hole courses (perhaps lighted) becoming a new phenomenon as an alternative to standard courses. Jack Nicklaus and others have long thought they could see a time in the future where 18 holes is just too big of a time commitment, and that was before smartphones etc.
Take the place of 18 hole courses? No not at all, however expose non or new golfers to the game in a potentially new way I can see happening. Maybe some type of lighted 9 hole course at a top golf.
Aside from that crazy idea, 9 hole courses are great for young golfers and building first tee programs around them are a good idea with a nice range. It is how many of us probably learned the game yes? I remember playing a 3 hole youth course when I was young carved out of a driving range. Thus, I appreciate these courses (some of which are private) constructing a 9 hole course along with their standard courses.