No, it means that person is not working only on Scala, or rather the current implementation of Scala. People can work on multiple projects over the course of a year/years.
> on a language that will "eventually" become the future of Scala
You changed "Is it the future Scala? Yes, it will be - eventually" (I think can best be reworded "eventually be the future Scala") to "eventually become the future of Scala." To me, those have different connotations. The former means that it's not finished yet, but when it is it will be the base of Scala at that time. The latter implies, to me, that at some time in the future this will be the base of Scala at some time further in the future.
> which means that, right now, dotty is not the future of Scala
And here's where that different meaning leads you wrong. dotty is the future of Scala right now, but it's not that future Scala yet.
> A lot of very smart people seem to be very excited about that, I can't help but find it ominous.
People are generally happy to have to the creator of something they like working on its future.
Scala is being maintained. Improvements and releases are being made in the meantime. More than one person can work on Scala, and a single person can work on multiple aspects of Scala. Big changes like dotty are being carefully planned and executed at the same time other changes are made. People are excited that Scala is continuing to evolve and becoming a better language, and that a beloved innovator/creator is playing a significant role in that.