I think this scenario are very similar to the affect that the Halving has on the Bitcoin price. By the time when the actual Halving happens, most of the price increase has already been "priced in" ...because people knew that the event would happen.
So, the ETF approval will have the same affect... where the perception will be that it will be approved and people will buy early to get cheaper coins, before the price increase.
Have the prices really already been priced in at the halving? I would argue now. Perhaps in the very short term you could consider that (e.g. 1-3 months?) but 9-12 months later it seems now. :-)
And I agree that the impact of the ETF approval may be priced in, but the impact of the ETF investments over time probably hasn't.
Who knows for sure though....ask me in 5 years. lol
:-)