I see more of a negative side here. With the current spread of fake news that becomes impossible to regulate, I can only imagine how far worse it`ll be in the future.
As neuralink is a network device, it raises the whole range of stuff related to it: malware, antiviruses, spam filters etc. which we we`ll have to account for.
As for learning 4 year info in 4 months, I`d not say it is exactly learning - you simply download information to your brain, but you lack your own logical conclusions that you obtain while you learn stuff traditional way.
I guess it will not be "learning" exactly. But if a virus is also "download" wouldn't it still be up to us to reject it the same way we could reject being brainwashed? Is the risk too high to have the ability to gain knowledge about something?
We still have no idea how the brain will react to receiving loads of information in a way that is so different from conventional learning, or any of its derivatives.
May be there will be no way to regulate what we receive via the Neurolink apart from software measures, as the brain itself won`t have capability to regulate incoming info?
Btw, we already have the ability to gain knowledge about anything. It is dependent on the amount of time we wish to spend, but it is still present.