I think the opposite. Passkey is limited in a lot of ways.
It will not be easy to switch from Android to iPhone at all and vice versa. It can be done, but it won't be easy at all.
The other issue is sharing Passkeys. My wife and share passwords for our bills, how can you do this with Passkey? You can't. This again where a password manager will shine. My wife can use the vault we share passwords, we can share Passkeys very easily.
Another issue is when you login into a computer and your Passkey is on your phone. Yes, there will be a QR code, scan with your phone, and log in, but password managers are cross platform. I have my Password Manger on all of my devices, so I can easily log into a website without having my phone with me. 1Password also made a way to log into a computer that isn't yours easily (article below), and I bet Bitwarden and others will follow.
Work Passwords... I read an article about work passwords, how this will be an issue (I wish I kept that article). It's probably not an issue now, because it will take years before Passkey takes off.
Password managers are superior in this way, and just switching/cross platforms alone are worth it.
Here is the article about how 1Password will handle Passkeys (and where I got the quote above). Please note, I bet money Bitwarden and others will do the same, and it's great. They will make it easy to switch Password Managers with Passkeys also.
Passwords aren't going away anytime soon, so password are going to be around for years. Not every wedsbite is going to change overnight to Passkey.