The biggest threat to Bitcoin is another cryptocurrency. I don't know which one that would be, but you can take a guess.
1. Nearly all publicly accessible cryptocurrency operators ('validators") are fundamentally non-state-organisations, or NGOs, equivalent to unregistered religious societies. The industry lingo for this is DAO : decentralised autonomous organisation. Unless states outlaw such organisational activities, publicly available cryptocurrencies get to exist. States are incentivised to keep these around, as a form of mutually-assured financial vulnerability. No state wants another state's fiat to be the fiat franca, therefore nearly all states currently implicitly support non-state-fiat by virtue of not outlawing non-state-fiat.
2. Bitcoin however, has an overly concentrated share-of-mind. Currently it holds about 60% of the entire asset class's capitalisation, a fraction which represents what the investment community at large knows about cryptocurrencies in general. One might say the same of gold, among other metals, so maybe this isn't going away. However Bitcoin is becoming more complicated in ownership, financially leveraged in the economy, and intertwined with other asset classes. Moreover, unlike gold, Bitcoin is subject to catastrophic failure via cartelisation of validators and the 51-percent-attack case.
3. Under what circumstances might large holders of Bitcoin be forced to sell their holdings? (Looking at you, $MSTR.) Every professional asset manager's RMD should have this contingency documented clearly. Under what circumstances might nation-states collectively agree to outlaw non-state-fiat? Ditto RMD fiduciary duty. Under what circumstances might an ex-Bitcoin cryptocurrency gain more economic momentum than Bitcoin? The RMDs must have a plan.
4. Pro-tip. RMDs never have comprehensive plans.
5. I guess we'll just wait and see how things develop.
6. Everyone can go back to work now.