Dawn’s Piplup can stay as it already is while Ash catches a wild one and evolves it all the way into Empoleon.
Yeah that's why I want Ash to get Piplup. If Chloe got it well.... that'll be it. It'll remain Piplup due to her Pokemon being on the cute and marketable side. Eevee'll likely be the only member to actually get development, seeing how often she gets episodes and we're almost certainly going to get an episode revolved around each Eeveelution(Hopefully not and they'll just combine some like potentially Volkner's Jolteon into other episodes like Ash's PWC match or another meet up with Gary to avoid repetition, and so Chloe actually has episodes about non-Eeveelutions)
With Ash, you don't really see his Pokemon all that often. Riolu and Farfetch'd were really the only exceptions but that changed once they evolved, so Piplup won't appear too much. My guess is they'd push it for a bit much like Riolu and Farfetch'd, then evolve it and it gets sidelined before they evolve it again. It's not like SM or the older sagas where you saw his Pokemon in every episode or just about, I mean Lucario is literally one of the most popular Pokemon in existence and vastly outscales Piplup yet we hardly see him! So Piplup's not going to just change that if Lucario's not showing up every few episodes, it isn't the Rowlet/Oshawott case at all.
If Ash got Piplup I think it's safe to say it'll go all the way, especially if the Sinnoh starters have a new Mega or something to show off.
It'd be the ideal scenario going the Empoleon route too cause
every Piplup acts the same... and Empoleon really didn't get that much screentime in DP. Paul and Ash had Torterra, Ash had Infernape, Barry had Empoleon but he appeared so late and didn't get many battle scenes with it.
I don't really think Goh's getting another starter, they'd surely have done that by now if he was given how much of a hard on the Kanto starters give staff and higher ups. I have a suspicion that they aren't allowed to treat starter Pokemon the way they do other Pokemon he gets, starter Pokemon always did get preferential treatment on the cast. Heck the same thing could apply to Pikachu hence why his evolved as fast as it did before falling into the void