There doesn't appear to have been any official announcements as of yet. However, I have heard through the grape vine that recently accepted founders with Canadi

There doesn't appear to have been any official announcements as of yet. However, I have heard through the grape vine that recently accepted founders with Canadian corps are being asked to re-domicile. You can also see the change by comparing the wayback machine post to the currently available version to see the removal of Canada. Hopefully we get more transparency from YC soon.