Death knell? Not necessarily. It sounds like the company is pivoting. That's what startups do, if they're not finding traction with their original idea.

It's perfectly fair to not be interested in the new direction of the company. If that's the case, then leave. But if you're just worried that the company is dying because it's changing direction...well, you should ask the founders how much time and money remain to try out the new idea. If they don't tell you, then that is a problem.