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

my guy friend and I were hanging out on Friday when he left i text him and asked if he wanted to hang out the next day and he said yes and how he wanted to "take me down".
I told him i was flattered but that i had a boyfriend i told him that i would like to get to know him and that if he still wanted to hang ill text him tomorrow which would be saturday. I text him today and asked him if he would like to hang out after he get out of work Sunday but then he said we'll see what does that mean?
what does it mean when a guy says "we'll see ".?
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