Pokemon Go and Pokemon Legends: Arceus are having a crossover that will see a variation of Voltorb, usually native to Hisui, arriving to Niantic's mobile game.
Hisui is a region that can be explored in Pokemon Legends: Arceus and it has its own variations of the Pokemon you may have seen before. One of them is Voltorb and the one appearing in Hisui will also appear in Pokemon Go now. Professor Willow is researching this species and its differences from the Kanto region Voltorb.
What all this means for POGO is that Voltorb and Hisuian Voltorb are now appearing in the wild. The latter will be around until the Lunar New Year festivities wrap up. Lucky trainers might run into a Shiny Voltorb but the Hisuian Voltorb can't evolve for the time being.
Furthermore, Pokemon found in the beginning of the Power Plant event will continue to appear in the wild.
Season of Heritage story is getting new chapters as it's revealed that Team GO Rocket's invasion was just a ruse in order to open the mysterious door. Now the trainers need to go in and start piecing clues together to figure out how to proceed.
One thing that Willow found behind Team GO Rocket's mess is a strange Poke Ball that contained the aforementioned Hisuian Voltorb.
Given the time discrepancy, it's suggested Team GO Rocket's shenanigans have something to do with Mythical Time Travel and trying to stop their plans will be the new special research with Professor WIllow.