Good question!
If interpreted literally, in theory this phrase does not rule out the possibility that the event might happen at some point later on.
However, in practice, if someone says, ''That's not gonna happen any time soon", it's usually clear that the speaker thinks that it will probably never happen.
In effect, this is a kind of understatement - one of many cases where what we 'say' is not exactly the same as what we 'mean'.