The new open world adventure Pokémon Legends: Arceus should introduce Fire-type or Water-type versions of Voltorb and Electrode, in order to match the new Poké Ball designs in the game. The world that debuted in Pokémon Red and Blue has been retconned over the years, thanks to the addition of elements in later games, such as new types, so there's definitely a precedent for this occuring.
The Kanto region was created in a bubble and the Pokémon world was gradually developed around it. This is why references to real-life animals and countries were present in the beginning, but then slowly removed from the franchise. The timeline of the Pokémon franchise is loose at best, except for a few instances where games are direct sequels. The fact that most Pokémon games have self-contained stories means that the timeline rarely crops up. The events of Pokémon Red and Blue aren't important to the protagonist of Pokémon Sword and Shield, so there doesn't need to be any connection between the games, outside of a few references.
Pokémon Legends: Arceus is an upcoming game that is set in the distant past of the Pokémon world. This means that fans will be given their first glimpse at what the Pokémon world looked like before the days of Pokémon Red and Blue. This brings up the question of what some Pokémon will look like, as their murky origins could be brought into focus for the first time.
Steam-Powered Poké Balls Have Implications For Voltorb
The official website for Pokémon Legends: Arceus has confirmed that the Poké Balls used in the game are far more primitive than the ones that fans will be familiar with. These retro Poké Balls are made of wood and powered by steam. This seems like a silly joke on the surface, but it raises questions about the Voltorb line. Those Pokémon are meant to resemble the Poké Balls from the Pokémon Red and Blue era, which is why they're Electric-type. If those modern Poké Ball designs don't exist yet, then does that mean the Voltorb line also doesn't exist?
One way in which the developers of Pokémon Legends: Arceus can include the Voltorb line is by giving them new Sinnoh forms. These versions of Voltorb and Electrode could be Fire-type, Water-type, or both, to reflect the fact that they're based on the steam-powered Poké Balls. It's also likely that they'd need new names to match their types, as they would no longer have an electricity theme. If these alternate versions become popular with the fans, then they could make an appearance in the mainline Pokémon games through the same method as Fossil Pokémon, with advanced technology restoring the ancient Voltorb/Electrode to life and letting them roll around the Pokémon world once more.
Pokémon Legends: Arceus will be available on Nintendo Switch in early 2022.