I think they finally got told from the higher ups to stop tweeting, because both John and Clint stopped tweeting at right around the same time (7 days apart in November). Kraelo still does because it's his job (and he's had some personal health issues in the last few months so his tweet volume is down too).
Writing's been on the wall for this for some time now, and I don't blame them when it gets to the point where anything they tweet meets a flood of negative backlash. Just not worth it at that point.