"So it may not be the new young readers and writers coming up who are more likely to be provincial in their tastes, but in fact members of our own generation(s) (I add the plural because the members of this site represent so many different age groups)."
Teresa, the "provincialism" I worry about was "temporal provincialism," which one sees when people won't or even can't read anything that's more than a few decades old.
I saw this develop in higher education. Anecdotal: I created a Literature of the Non-Western World course for my very small state university. When I taught it, the students got at least some exposure to the Mahabharata, they read Arthur Waley's retelling of Wu Ch'Eng-En's Journey to the West (i.e. they read Monkey), they read Japanese folktales as retold by Lafcadio Hearn, etc. -- as well, to be sure, as 20th-century works. The department hired a new professor upon the departure of a predecessor. I was really impressed by her having taught in China, etc.; though I liked teaching LNWW, I offered the course to her. Well, it was her course, no strings attached. But the impression I have is that she taught it basically just as a "multiculti" course in which all of the works were recent -- maybe The Kite Runner and so on. So the course had become temporally, or chronologically, provincial.
In my view, students, especially English majors, really need to read a lot of early literature. I would be pretty receptive to the idea that they should read anything after, say, Ulysses on their own, not in their courses. Do they really need to study, say, Byatt or Amis (either one) or McEwan or Grace Paley or Cormac McCarthy in college, if that means they do not read much from (say) the 17th century? I myself am a case in point; basically I never read Milton in college, had to study him on my own (also his fellow 17th-century authors Browne, Bunyan, &c.) I was in college in the 70s and 80s. This sort of thing has only gotten worse, so far as I can tell, since then. Anecdotal: my little college hosted a "conference" on "early British literature" a few years ago. (I have mentioned this before, here at Chrons.) Now I would take "early English literature" to be, you know, Beowulf, "The Dream of the Rood," Chaucer, Sir Gawain, maybe Malory. But from what I saw "early" could include even, say, D. H. Lawrence (!? -- died 1930). Memory might be deceiving me -- is that really possible? Lawrence? But you get my drift.
That's what I'm getting at about temporal or chronological provincialism. Sf is a special case because, really, the genre hardly gets going till the late 1800s.
Some of what I've written here is something of a digression from the topic we were discussing, about present tense narration. Anyway: the habitual and pervasive use of present tense narration is a very recent thing. If that becomes the norm for young readers, if that's what they expect most imaginative literature to be like, then the great majority of literature in English, which is not written in present tense,* is likely to become that much more alien. We shall have readers who know the airports of Amsterdam and New York, Beijing and Saigon, Istanbul and Buenos Aires, but are terribly provincial as readers.
*I have the impression also that more and more readers struggle with, say, The Lord of the Rings -- they find their minds wander during the "walking bits" and so on. Now why would that be a problem?