People can get your DNA without your consent already, as your DNA gets onto every object you touch. The most valuable part about sending stuff to a DNA company is your consent, especially considering that sequencing costs have a super-moore's law like cost reduction. Once they have your consent they can share it, sell it, rent it, to recruiters for ad targeting, insurances, etc etc. Without consent they'd get onto dubious legal territory, if e.g. Amazon took gene samples from refunds. But maybe it'll just become part of their TOS, you not being able to opt out unless you don't want to refund your stuff to Amazon.

Not sure if the ability to sequence DNA yourself is really beneficial to privacy, after all that allows people to sequence the DNA of many people around them.