Yes, it is.
ed25519 depends upon discrete log for its security, which Shor's algorithm can (theoretically, of course, not like it's ever been done) efficiently solve.
The post-quantum algorithms are in active research right now.
I don't blame anyone for avoiding those at least until we've quantum computers big enough to solve baby toy elliptic curves.
Yes, though OpenSSH has already switched to a quantum resistant algorithm for key exchange (Streamlined NTRU Prime, combined with x25519 in case SNTRUPrime turns out to be weak), and that's the stuff that needs to be switched as soon as possible to preserve forward secrecy. Authentication keys are less urgent.