The events in All Good Things were the result of Q playing around with reality (or possibly just Picard) by moving things backwards, forwards, and sideways through time. The presence of Q and his usual shenanigans means that all bets are off as to what is real, what isn't real, what will be real, and what might become real.
The future events in All Good Things were just one possible future. Q chose or created that particular future to see if Picard could step outside of his limited human view of time and reality. Also keep in mind that the events shown during the Farpoint mission didn't happen in the past-as-we-know-it either.
Time travel is all wibbly wobbly timey wimey and doubly so when Q is involved.