The post clearly states that users can install extensions through the developer's website. The main difference here is that extensions cannot be silently installed — users have to explicitly install them.
Sounds good to me. No more annoying adware extensions.
I agree regarding adware, I think its just a poorly written post in terms of clarity. It could have been better summarised as
We are removing sideloading (The ability to silently install extensions from your local machine as an xpi file)
- This will not affect the ability to manually install extensions, they will need to be installed from a source code directory (Link to chrome post on same)
- This makes users safer (Malicious extensions will need to be approved and installed by a user)
- This makes it more obvious when an extension is installed (Confirmation dialog)
Sounds good to me. No more annoying adware extensions.