Just read an interesting article on how quantum computing can break not only Bitcoin signatures, but also hashing from mining.
IMHO Bitcoin's stumble from #1 will be because of two things:
- Quantum computing
- Security budget issues
1 isn't because you can't solve QC attacks on signatures and hashing, but because you have to change stuff to do it.
Bitcoin is notoriously change-resistant, and lots of people's stuff will break if it does: like people's funds being left in old addresses and getting stolen by QC attacks, or ASICs getting bricked by needing to change hashing algo.
The upheaval from hard fork changes will disrupt its "safest crypto" reputation, permanently.
Here's the article: