According to our friends at Pokeminers, the assets for Kyurem, Black Kyurem, and White Kyurem have been updated.
It's generally considered to be normal for a Legendary Pokemon to have its assets updated before its initial release, but the asset update for Kyurem-White and Kyurem-Black is a bit surprising as we have not had any announcement as to their arrival or hint that they could be coming. It's possible that this was just done due to these two formes being connected to the base-forme Kyurem, but it's also possible that they may be showing up sooner than expected. Perhaps in relation to Go Fest 2020? The coming days could be exciting!