We've already drastically changed the way history is taught to accommodate the ever-growing body of scholarship. In the 19th century, most of the history anyone would learn at university would probably consist mostly of European political history at the exclusion of almost every other modern subdiscipline. Now, undergraduates, and even high schoolers to some extent, have to choose to specialize in a few areas: maybe one or two continents, one time period, and one thematic glaze e.g. economic history, gender history, etc. I suspect that future research will just follow this trend and everybody will become more and more subspecialized. By any means, nobody can ever hope to learn ALL of history! The best work is produced by historians simply following their interests rather than attempting to sum up millennia of human history from all around the world in a single lifetime of scholarship. And in my opinion students of history should similarly follow their interests, reading whatever happens to catch their fancy, which usually leads to more and more in-depth research as well as broader contextualization as the student is exposed to a wider body of literature.

There is already a massive amount of history that isn't taught in schools, from long ago time periods, and also simply other places around the globe. From my experience of the English educational system, the focus was entirely on British history, and even then I spent considerably more time studying aspects of history which were considered to be the most relevant by today's standards or what has had the most recent great impact. Most schools focus on WWI and WWII more than any other time period, so I imagine that in the future, other time periods of great events will become "popular" and others won't be taught at all.