Hi Andrea, welcome back How you have you been? Have you seen our new homepage with your profile?
As for the question at hand, I think it depends on when the actual process of seeing each other is happening. If it’ll be in the future the second sentence is the correct one. But what about if the event is happening at the moment of speaking?
For me the difference is between authority and regret. Let me explain -
The last time I see you - suggests that it is final because you have decided that you never see the other person again or you have been told or instructed never to see the other person.
The last time I’ll see you - suggests regret because circumstance such as living a long way away prevent you from meeting again.