2 for 2 in Alola pics!

If you watched the 6th generation series, I don't need to tell you the Serena had feelings for Ash. The writers did a good job at making hints obvious. Taking those hints into account, I conclude that Serena is the intended end game for Ash. Now before you start your rage comments, let me give you a few, non-anime reasons.

At the start of XY, it had been over 10 years since we saw Misty, and the average Pokémon fan wasn't old enough to ever remember Misty. She hadn't become irrelevant, it just would seem out of nowhere to bring a character back for Ash that nobody even knew. Like I said in the disclaimer, it makes more sense to pair him with someone who he had a lot of time to develop a relationship with, and Misty had been gone for too long for viewers to see a meaningful connection between them.

Why did they need a replacement for Misty? The gen 5 series was very unpopular, and views declined substantially from previous seasons, so it's only natural to prepare for the end of the show. Though it would have been easy to write Ash going back to Kanto, and finding his end there, after XYZ, Ash had been gone for over 2 years, since there was no gap between gen 5 and 6 that could warrant a reset, Ash came home for a day, changed clothes, and the left for Kalos. He did meet with a few friends, but the time away wouldn't allow for an instant reunion as if nothing changed, relationships just don't work like that, especially romantic ones. As much as people say, absence does not make the heart grow fonder.

That's the story reason, now here is the business reason. Serena made so much money for the Pokémon company, and still would if they brought some aspect of her back through more merchandise, or anything else, she would print them money. But there is one huge problem, a contradiction. If they brought her back for the purpose of the end of Ash's journey, they may get enough money to keep the show going, just maybe. Also, Pokémon has showed they are not above a little fan service, and that she definitely was. I hate to tear down a character as loved as her, but when you look at the facts, it's hard to deny that Serena is a replacement for Misty, and free money for the Pokémon company. We can also throw in the interview with the writers which state that viewers are supposed to hope they end up together, for fun.

Again, if you want all the moments, go to bulbapedia, but I'm only going to name a few.

Miette. That was her only purpose. She existed for the sole reason of teasing Serena about her feelings toward Ash.

Their first meeting: before she even finds Ash, Serena is hoping and fantasizing about her reunion with Ash.

In conclusion, the entire gen 6 series was fan service(though I'm not complaining), and Serena is currently the intended pairing for Ash.