They're certainly going that way. Group DMs don't work with the API (in that there's not even a "hey log onto the website your client doesn't support this" notification). A ton of features have been removed from or gimped in the API, to the point where many of the third-party devs have given up.

"Fully disable" - probably not. But they'll certainly make it nearly impossible to produce something "like the Twitter app but better".