It doesn't void copyright.
Anyone that uses code that Copilot spits out which infringes on someone else's copyright is still liable. There's no requirement for intent. That may be a mitigating factor in terms of remediation, but it cannot void the copyright itself.
It can, however, produce a plague of completely ignorant copyright infringement, and since the user of Copilot has no idea where the code is coming from, there's no way to check if it was trained on infringing code.
If I used Copilot I would be real worried about the legal implications for me and that I could easily be accused of copyright infringement or plagiarism[*]. Of course people seem to not really care these days if they can cheat to get ahead so this is probably a feature, and 99.9% of user won't have their reputations ruined by using it.
[*] Although I'm personally more worried about the fact that most of the code will be wikipedia/blogs-quality and filled with bugs, edge cases and performance issues.