I agree with FumbleFingers' comment that the progressive can be used as a substitute for the future tense, and here isn't stopping has much the same meaning as won't stop and won't be stopping.
However, I don't think these have exactly the same thing, and can actually have very different meanings in a different context. Consider these three examples:
The train isn't stopping.
This implies that the train was expected to stop but currently is not. Perhaps it's a runaway train. Perhaps the driver just forgot to stop. Either way, the train is still moving. You can also use this to imply the train is going to keep moving, no matter what, "This train isn't stopping for anything!"
The train won't stop.
Without additional context, this implies some kind of inability to stop moving ("I can't stop the train!"), or sometimes the expectation that it will keep moving until some condition is reached, for example, "This train won't stop until it reaches its destination."
The train won't be stopping.
This is a common expression used to explain an expected future behavior of the train, for example, "This train won't be stopping in Chicago."
In your example, the author's use of "isn't stopping" is a little like the runaway train in the first example. Most people would have stopped by now, but this guy keeps going and going.