Satoshi for me looks like Banksy, an artist that don't show your face and maybe this increase their art "value", so Satoshi can be here working with other alias... so let's go to the question:
What could happen if Satoshi appears?
If he start to appearing on media and things like that, can pump the coin?
If he's an criminal or something like that, it can dump the coin?
I think wheather Satoshi discloses his identity or not,it is not going to affect bitcoin price much unless he decides to sell hi stored bitcoin which he can do without going to public anyway.
I also believe that Satoshi is not one single individual because it is hard for any human being to resist the temptation of getting all the money and fame for such a long period of time
Do you think Satoshi isn't a human person? So is he an alien?
I think he is a smart guy that is rich now anonymously, but I think also that he influences the market a lot. Nobody knows who he is, so he can be anyone from any country, he can be a chinese and can be acting at their favour as we are seeing the chinese power in relation to Bitcoins.
Anyway, we have much to thanks to him and to all others that helped him in this project.