Split/Second was a damn good game and Black Rock Studios is a damn good developer.
Unfortunately, that just isn't always enough to warrant a sequel. According to a recent report , Black Rock has been forced to cut its staff significantly, and this comes after canceling work on Split/Second 2 last December. The source also states that over 100 jobs are at risk and only 40 are safe, which means this developer will be a shadow of its former self if Disney Interactive really cleans house. It seems "concept pitches clearly haven't gone well" since then, and they were unable to nail down a project for some time. For instance, one possibility had been a follow-up to 2008's excellent Pure , but that didn't fly, either.
So it seems Black Rock is working on only one game, and that's how Disney wants it: one game at a time. We're not aware of that new project yet, but it has been described as "promising" and "new and risky." This one had better be a winner because if not, it could very well be the last title Black Rock Studios ever produces.