First of all, Bitcoin is a decentralized protocol with no one in control. It doesn’t and can’t have any plans or roadmap, and any changes to it require consensus of its users.
With that out of the way, I don’t think quantum computing is seen as an imminent threat. From what I could find, even optimistic predictions place practical quantum computing at least 10 years from now, and it’s not a given it’ll even ever be achieved.
On the other hand, quantum-resistant signature schemes use much larger public keys and/or signatures, which would seriously limit transaction throughput. According to a recent blog post from Ledger, the state of the art PQC scheme uses 1563-byte signatures, more than 20 times larger than the signatures currently used in Bitcoin. Since this is an area of active research, I expect people will want to wait for more improvements before committing to adding a specific scheme to Bitcoin.
