It's tricky to say when something like this could jump from...

It's tricky to say when something like this could jump from proof of concept to being out in the wild because a lot depends on what the author's motives are and whether he wants to send it far and wide or if he just wants to show how good he is. The spread of viruses also depends on what people do with their phones. If they are only making calls, it's unlikely they will get infected.