What is going to happen in the foreseeable future? I have no idea, but here are a few guesses, as and when they occur to me:
There is a lot of interest in the English Defence at the moment, as a reply to 1 c4. Whereas this opening used to be the domain of the more 'eccentric', or original, players, such as Jon Speelman, it is beginning to filter down to the lower levels, and to 'more mundane' wood-pushers.
The type of position Black obtains with ease in TK158 helps to explain why, perhaps. Black, who has recently written a book on this opening, quickly gains control of d4, and never lets go.
Another reason is the tactical chances that Black may gain, particularly on the f-file after he plays ...f5, but also elsewhere, as TK154shows.
Anyway, for more detail on this line see the eBook.
The line 1 c4 e5 2 Nc3 Nf6 3 Nf3 Nc6 4 g3 Nd4 (see the Four Knights, eBook) will start to catch-on amongst non-GMs, as will the line 1 c4 c5 2 Nf3 Nc6 3 Nc3 Nd4!? (see the Symmetric eBook). Why? I think that they are relatively simple to play, and allow Black a straightforward development plan, whilst avoiding the most theoretical stuff. The only real problem with this last line (as I discovered myself) is the move 4 Ng1 when Black has to either accept a repetition of moves (with 4...Nc6 5 Nf3) or play another line (like 4...e5 5 e3 Nc6).
Certainly for those players who have a Slav or Queen's Gambit in their repertoire, and can answer 1 Nf3 with 1...d5, I think that the Capablanca lines where Black delays playing his king's knight to f6, and brings it to e7 instead, are a good bet.
For those who wish to play Larsen's Opening, but don't wish to allow 1...e5 as a reply, taking a 'Réti route' and playing first 1 Nf3, and only then 2 b3, is becoming more, and more popular.