What does it mean when a guy says "we'll see..."

I was talking to a guy I was interested in and he knows that I am into him; we are friends and he says he isn't looking. That's fine but then the friendship became a little rocky. I didn't feel as if he was my friend, he was detached a lot. I confronted him and asked if he hated me, he said no... at the end of the conversation I said I hope everything is gonna be fine and he said don't worry everything will be, I interrupted and said "fine with us" he said we'll see...
What does it mean when a guy says "we'll see..."
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