Well, think about it. In House of M #7, Wanda literally re-wrote all of reality to erase mutants from the world (Doctor Strange used his powers to slow her down, so he protected roughly 1,000 mutants from being wiped out, but millions of them lost their X-Gene)...
This briefly made it so that she, Magneto and Quicksilver were all no longer mutants.
However, think about it, she flat out USED HER REALITY ALTERING POWERS to make it so that she was not a mutant anymore.
How, then, can we possibly believe anything that has happened since then? The comics say that Magneto is no longer her dad and that she and Quicksilver are no longer mutants, but couldn't that just be a case of residual effects of Scarlet Witch using her own reality-altering powers?
We all know that the REAL reason Scarlet Witch and Quicksilver stopped being mutants is because they were going to be used in the Marvel Cinematic Universe and as part of a deal between Marvel Studios and Fox, the MCU was not allowed to use mutants (or say that they were the kids of Magneto), while Quicksilver appeared in the X-Men films as the mutant son of Magneto.
Once that happened, Marvel figured that it should just make that change in the comics, as well.
Now that Disney owns Fox's movie studios, though, that isn't an issue anymore.
So just reveal that Scarlet Witch used her powers to alter reality so that she and Quicksilver were no longer mutants and then have reality altered back so that they are both mutants and Magneto's kids. We can keep Robinson's retcon and just have it be that Magneto is their father and the witch lady is their mom. Magneto's wife had left him, after all, so he was out there single for a while becoming a great geneticist somehow, so he could have easily met and had sex with their mom.
So just get it done, Marvel! Scarlet Witch and Quicksilver NOT being mutants doesn't really serve any purpose.
Okay, that's it for this installment! If you have a suggestion for a retcon that YOU'D like to see, drop me a line at firstname.lastname@example.org!