They could sell Aubameyang to China, but I read in a kicker report about Leverkusens Kevin Kampl (former Leverkusen coach Roger Schmidt is now coaching in China and wants him badly) that Chinese clubs have to pay a transfer penalty which is the exact sum of the transfer sum and Leverkusen doesn´t want to deal with the creative tricks of the possible Kampl transfer (whatever that meant; possibly delaying the payments to lower the penalty, I don´t know).
So after the 3week layoff (he signed with us; we don´t want him; I want to move to China!; You´re not training with us anymore, clear your head before you move to China!; I want to participate in Cologne´s training, and I will go to court with that!; finally all parties agreed to a 35mil-€-transfer), Tony Modeste moves to China. Leverkusen seems to stay away from that problem (China´s transfer deadline is tomorrow, Friday) and Dortmund doesn´t even talk about that location, as the money would be insane.
So there isn´t much left for Aubameyang. And as someone said before, he isn´t a versatile player. He can finish crosses and can finish off the dribble and counters. I don´t see age as a problem, when you look around Europe and the money spent (think last year for Higuain). So the biggest downer for me is that he isn´t a back-to-goal player, which you probably need or at least want in many big clubs which are dominating possession, at least in theory. This would probably all play out better than expected I guess. But he´s no Lewandowski as a CF. Dortmunds system suits him just perfect. I doubt he will score 30 league goals at PSG or Chelsea, even as the central point of their offense.
If he doesn´t like new coach Bosz or what he has seen in training/preseason (like if he tried to install a passheavy 70% possession, which I doubt he will), then he wants to be gone. But Dortmund would have a ton of trouble to replace his productivity and experience, as Reus and Guerreiro are (again) injured for months, so they should be reluctant to do anything.