First understand the basics of ETF. There are several types of ETF but the major types are Physical and Synthetic. The physical ETF deals in real underlying asset, that means a physical ETF actually buys the underlying asset from the market. Whereas, a synthetic ETF usually deals in futures contracts of the underlying assets without actually buying the product from the market.
So you need to understand what kind of bitcoin ETF is actually being approved! If you see a synthetic bitcoin ETF has been approved, don't expect any impact on the market because the managing company is not going to buy any physical bitcoin. They will just buy bitcoin future contracts as an underlying asset.
However, if you see that a physical ETF has been approved, you can certainly expect a good spike in price because then physical bitcoins will be bought from the market by the managing company. It will create fresh fund inflow and increase the demand in the market.
I am not very optimistic with this ETF thing because several companies have shown their interest, but only Winklevoss ETF was the physical one. Rest all were synthetic.
It is true what you say, only physical BTC ETF can seriously affect the market, but we do not know in what way big investors will react on ETF approval. Some general opinion is that big money should enter in crypto market, but we can not be sure that this will happen. BTC ETF is just easy way to invest, but some other things need to be regulated before BTC attract big money. By the way, Winklevoss ETF was not physical - you probably think on VanEck-SolidX Bitcoin ETF.
I agree with you, Bakkt should be big thing for BTC and it is 100% sure that will certainly happen before the end of this year. Maybe the crypto community did not recognize enough the potential of this project, and I am sure many never heard for that. However we will see soon if Bakkt can make some significant changes in cryptocurrency world.