Maybe. You could ask on Twitter (would have to be a y/n question).
Realistically, if he were going to do a HFT book with a couple options per class... at two weeks per subclass that's 48 weeks before he finishes. Before playtesting, which can take several months.
But to fill an entire book they need a lot of options: twice as many as will actually make it into the book so you can test and pick the best options. Now we're looking at 96 weeks of design.
But he's just grabbing whatever suggestion from Twitter catch his interest. That's not going to lead to the most popular designs. And he's likely only going to do one per class before moving onto races and spells and other design elements.
They do have the time though. I can't imagine them releasing a book with more class content before 2019. Or 2020. A few of these options might be tested for that book, but whether or nor they make it in would depend on if it's well received by the entire community via surveys.