My understanding is that this repeals a law which was passed at the end of the Obama administration which never actually went into effect. If that's the case, it's already been happening - this bill just brought the issue front and center.

The regulations that are being repealed were passed on October of 2016, so data-hungry companies already have whatever browsing history you gave them.

It's been legal to do so since 2015 and through next December at a minimum. That is the status the new administration inherited.

The removed rule wasn't slated to go in to affect until 2018.

Edit: The rule was intended to stop existing practices or prevent companies from doing this in the future.