Repealing the Obama rule does mean that you can't opt out of data collection or sale. It does not mean that your individual browsing records are available to anyone with enough cash. Moreover, much of the rules Trump's executive order overturn had either very recently taken effect, or not yet taken effect.
There may be much theoretical damage from overturning the regulations, but the practical effect here will be minimal, and limited because of the other laws that already exist to prevent exactly the doomsday scenario many are predicting.
I'm not saying that Trump isn't after your privacy rights, but the surest test of that will be whether or not he goes after or seeks to circumvent the 1984 protections I referenced earlier.