When I was talking to a native American English speaker, he seemed to use this sentence "we'll see", if I am not mistaken, to signal a closure of our conversation. The conversation was amusing, no sign of hostility or anything negative. And I did not raise any question. According to the context then, I understand it as something like "we will meet sometime somewhere again". But as I searched about the sentence, I only found definitions that are not relevant to the my context. So I would like to know what happened?
It depends on what your last comment was. If you had said "I'd like us to have dinner together", his response may have meant, I have to wait and know more about my work schedule, and see how much money I've got to see if I can pay for dinner - I will just have to wait and see!
If your last comment was "I wonder what the weather will be like next week", his response again, may have meant we have to wait and see because we can't predict the weather.
But he may have had really nothing to say or add to the conversation and was rearing to go home to his girlfriend and wanted to end the conversation, instead of keeping it going on and on.
It all depends on what you guys had been talking about, and what he was thinking in his mind that he wasn't sharing.