I think it's pretty simple.  The strategy is to increase BTC per share.  To do this it relies on a constant stream of new investors to by new shares at an ever increasing premium (or buy convertible bonds to accomplish the same thing).  Inevitably, it will run out of new investors, and the later investors will have effectively bought really expensive BTC so that the earlier investors could have really cheap BTC. 

 The thing is that its not actually Bitcoin that they're buying. 

 Yeah, probably just Coinbase IOUs.