The best time to buy is now. ETF is due 3 days from now, and it's more likely to be approved than not. So there's a huge possibility of price kick-off upon its announcement. Prepare for a rally!
Some ETF have already been denied yesterday by the SEC, I wonder why people keep thinking this is going to be approved that soon, yes there is a lot of support from the community and even many institutional investors want to see this but the SEC seems completely opposed to the idea, if you want a bull market then you will have to wait until it originates from within the community and not due to an external source.