Firstly, as the letter notes, the majority of people using TypeSafe/LightBend's services are in fact "traditional" Java shops. This suggests that - in the enterprise at least - there's limited Scala penetration.
Secondly, the move to a more generic name (LightBend) is one more step away from their core competency. The name TypeSafe was chosen to highlight a particular aspect of the platform they felt was important. Although they likely still do, their customers don't appear to appreciate it (or at least in the same way it was meant, as an advert for Scala).
Finally the bifurcation of technical resources between ongoing Scala development and Dotty as a research project are likely to come up short in both regards. We are on the cusp of Java 9 being released within the year and Scala's big backwards incompatible step forwards with Java 8 still hasn't happened.
At the least you'd have to be a gambling person with a penchant for long odds to continue with Scala at this point.