I've decided to make some unofficial predictions about language in the future based on today's trends. Some may come true, some later, and perhaps none will ever come true. Still, it can be fun to speculate:
1) The ban on ending questions with prepositions will become archaic. When I was a child, I was taught never to end a question with a preposition. It should never be "who are you speaking for?" but "for whom are you waiting?" While this tends to still be true in formal business and academic writing, in informal writing and conversational speech, prepositions seem to come at the end of questions more often than not unless the speaker is especially careful about "correct speech" and/or is a language prescriptionist. However, even in some recent English teaching worksheets for non-native speakers, I was surprised to see it listed as allowable to end questions with prepositions. In certain other Germanic languages (to which English belongs), it is (and has been perfectly acceptable) to end questions with prepositions; Norwegian is one such example, as far as I know. In other Germanic languages, such as German, as well as the Romance and Slavic languages, the ban tends to persist in formal and informal writing and speech.
Nevertheless, this "schoolmarmish" rule in English appears to be dying out as it seems unnecessarily stilted and rigid, and I predict that in 50-100 years, even formal academic and business writing will reflect what is patently obvious in conversational speech.
2) This brings us to the next prediction: the loss of the word "whom." This accusative/dative form of "who' is one of the last vestiges of the English case system, which was, in the past more complex, more along the lines of the modern German or Slavic case systems. However, the use of "whom" mirrors the "proper" placement of prepositions in questions, and these days "whom" seems to be limited to formal business and academic writing in English and the speech of very meticulous grammar enthusiasts, who are in the minority. Its days are numbered. But those who are nostalgic for the once vibrant case system of English shouldn't be too disappointed, as cases will likely continue to remain alive and well in personal pronouns (I/my/mine/me, you/yours/your, he/his/him, she/hers/her, it/its, we/our/ours/us, they/their/theirs/them) and in the possessive apostrophe-s or s-apostrophe added to singular and plural nouns.
3) The complete merger of the subjunctive mood in English with the simple past tense. Today the subjunctive (contrary-to-fact) mood in English, which is highly complex in some languages, such many of the Romance languages, is mostly identical to other tenses, such as the past tense ("I wish he had it"), but in some cases, there are differences, most notably with "to be" (the traditional prescriptionist form being "I wish I were" rather than "I wish I was"). However, again, the use of "were" (which is historically similar to the German subjunctiv) in such cases is becoming increasingly relegated to formal and academic contexts and the speech of those who consciously wish to adhere to the rules and speak "properly." I predict that it will become archaic and fall out of use.
4) Profanity will likely become less "profane." I predict that so-called "swear words" in English will lose much of their taboo status and become more permissible in a greater number of contexts and arenas. This will, in my opinion, be the result of an increasingly less formal society in general (along the lines of women no longer wearing white gloves to public functions and the observation that far fewer people '"dress up" for air travel).
5) The ever-growing influence of technology and popular culture on English due to increased media saturation. In fact, I would guess that, over the next few decades, most new words entering English will reflect both of these spheres, some words becoming permanent fixtures of the linguistic landscape and perhaps being extended metaphorically. For instance, maybe the "Facebook verb" "to friend" ("to add someone as a friend") will gradually replace the current "to befriend" as the verb of choice when referring to act of establishing a friendship. It's possible! SMS-style shorthand, such as "u" for "you" and "lol" for "laughing out loud" will likely be around for a long time, but I doubt that these forms will become mainstream in anything but informal settings, at least not anytime soon.
6) Increased standardization of English. When I took linguistic classes as an undergraduate, I was exposed to the theory that dialects of English will eventually develop into their own distinct languages, just as dialects of Latin have developed into French, Spanish, Portuguese, Italian, and so on. The theory hypothesized that eventually there will be separate British, Canadian, American, and Australian languages, among others. However, what the theory seemingly failed to consider was that the countries (and dialects) of the Anglosphere (collection of English-speaking nations) are far less isolated on a daily basis than the constituent territories of the Roman Empire. Due to the pervasive global media, English speakers all over the world can log on or turn on various devices and be exposed to (or flooded with) English from all over the world. I believe that this cross-exposure will lead to the various Englishes borrowing more from each other and becoming more alike, with each dialect retaining some of its "quirks."
7) The increased use of English around the world. It seems hard to imagine how this could be possible, as English is today's lingua franca, but I predict that English will continue its sweep across the globe, with increasingly fewer non-English speakers. I'll also forecast that a number of historically non-English-speaking countries with large numbers of speakers of English as a second language will legally adopt English as an official language, alongside the historical national language(s), as a nod at internationalization (perhaps the Netherlands and at least one of the Scandinavian countries) or as a "neutral" compromise between rival officially national languages (such as Switzerland).
Some of these predictions may seem extremely obvious, but it is still useful, in my view, to view them as part of the dynamics of language change in English, which is going on as we speak!
(Posted by language fan and friend Silas McCracken.)