As the journey continues
Golurk is too big to be everywhere and can’t possibly manage all the potential chaos at once especially given its potential to be nearly unstoppable if it goes beserk. Cinderace has also commonly be used as a defacto leader even when they’re not out traveling. Cinderace is obviously going to get the majority of the focus as his starter but because his most consistent Pokémon are the faces of the Gen; the starters.Goh’s Golurk already serves that role in the lab, again Goh’s Cinderrace is more like Pikachu then Bulbasaur. It is Goh’s go to Pokémon, it is the only Pokémon out of all the Pokémon that he owns that he uses on the most consistent basis, in fact Cinderrace will be his only Pokémon that he uses in this upcoming arc. Every character that has been a previous companion that has a starter mon as their first Pokémon and partner such as May, Dawn, Serena, Lana didn’t replace their Pokémon or leave their Pokémon for another Gen starter of the same type and that’s why I can’t see Goh just leaving Cinderrace when it is first Pokémon and it will be the Pokémon that he uses if and when he catches Mew. Hopefully this series is longer then three years so they can show off even more Pokémon.
Again, all of the companions you mentioned lasted one season so why would they need to replace them? Why would May need to replace her Blaziken if she was replaced with Dawn for DP? I can easily see him leaving it behind.