Alex Died...McCandless lived and Mick Jagger is still a bad guy.
This could very well be possible. I know its probably my imgination, but if they where to make a sequel, they could have it this way. Let me explain.
The code he recited at the end could of been correct and the transfer was complete. The whole scene about the driving slip-up and the "I lied" stuff by Mick could of been set up by MCcandless to trick Julie into thinking that transfer was not a success, so she would love him. Think about it. If you were in that position, you would know that there is no way Julie would ever love you for what you did. So why not trick Julie into thinking your the real deal and the transfer was unsuccessful? That way she would be in love with you and you would get what you want.