The second that decision is made and released, I'm buying if rule change is approved for ETF. It'll be shooting up likely but still will only have upside in future. Holding off until then also but keeping close eye on it. If rule change is denied, then we'll see a pretty large $200-300 drop at least in my opinion for a bit.
I never wait till something happens to start buying. I always make sure I buy far in advance of everything where I purely focus on Bitcoin's growth. If you wait till the day the ETF gets approved, you're most likely already too late to benefit from the pump. In case the ETF gets disapproved we'll most likely experience a dump, but I don't expect it to be a heavy one. If the price tanks heavily after disapproval, it would mean that current increase is purely focused at the approval of the ETF. I believe current growth comes mostly from the increased demand.