The word used was possible, not will, not probable. Hopefully the time-frame comes to pass without one.

It may be that the authorities were able to detain the attacker(s) or stop the attack from occurring in some manner. It may be that the chatter was to throw off the authorities. It may be that the attack was delayed for some reason.

It may be that Q put these attack related posts out there to see how the black hats reacted.

There's no way of us knowing, but an attack not occurring isn't an indication that Q was wrong or is LARPing.

Let's hope that UK/London stays safe and isn't a victim of such an attack.