Widespread adoption by major economies like the US. Replacing the USD with Bitcoin is a radical notion, with significant economic and technological hurdles. The "unlimited supply" of USD as a weakness, but replacing it with a finite asset like Bitcoin presents its own challenges. Imagine a society where the money supply is inflexible, potentially hindering economic growth.
Blackrock's purchase of Bitcoin is a case in point. It represents a diversification strategy, not necessarily a mass adoption of Bitcoin as a transactional currency. People do need oil, but widespread use of electric vehicles could disrupt the oil market. Similarly, alternative cryptocurrencies like LTC or Doge could challenge Bitcoin's dominance for everyday transactions.
I don't think that the US will make Bitcoin or at least other currency to replace their dollar. It's a radical change and it won't simply happen. US, despite who will be the sitting President and what party he/she is, they won't abide by that. Good thing if they will support Bitcoin but so far that is not the case.
Blackrock is a huge financial entity, trillions worth, but I also doubt that they will let crypto takes over. For them it's business as usual, if they can make money out of it and continue to dominate the world order then they will jump on the hype and that's what they are doing right now.