Please do NOT deprecate SteemConnect!
I've always used SteemConnect for Login.

What if my device and/or webbrowser doesn't support the Keychain extension?

Also, what about the users who don't want or aren't allowed to install Keychain (e.g. because they're using someone else's computer)?

Do these people have to use the website's own login feature, which is likely to be less secure than SteemConnect?