IPNS names are based on public keys. A sybil attack can't make an IPNS name resolve to an arbitrary attacker-chosen value because the attacker can't make signatures for the public key.
A sybil attack could be used to cause part of the network to see a recent old value for an IPNS name, but clients keeping recent values cached for a while is already something that happens naturally, so it just seems like a more minor example of the general problem that a sybil attack could do a denial-of-service.
A sybil attack could be used to cause part of the network to see a recent old value for an IPNS name, but clients keeping recent values cached for a while is already something that happens naturally, so it just seems like a more minor example of the general problem that a sybil attack could do a denial-of-service.