An ETF has zero effect on the Bitcoin technology. It will be subject to market manipulation like everything else in the market. People who thought they were whales will in fact be fish.
However: the BTC futures ETF already has use cases for price suppression, so we're there already. Blackrock asking for a spot ETF is still a major improvement, and it's still an absolutely necessary stage of Bitcoin growth.
Before price suppression, big big bags will buy in (the biggest?). The halvings will still occur. Scarcity will increase. Bitcoin will become more popular and its use will likely increase. It will still be a tool for sovereignty and an alternative economic rail.
This is also an incremental step towards the ultimate test: nation-state attack. And every minute that passes, the network gets stronger.
As with many things Bitcoin and crypto in general, it's all about time horizon.