Quoted By:
So I think Ash is going to win the League and Serena is going to become Kalos Queen.
Hear me out on this one. Why would they throw in that scene of Elle and Yashio at the end of the previous episode if Serena were to lose the Master Class? They both are talking about some new Performer that is meeting their expectations and they both are encouraging her to strive for the Master Class in order to become the next Kalos Queen. With May and Dawn, this kind of build up wasn't present.
And as for Ash, other than the fact that I don't think the writers would let Serena succeed in her goal and leave Ash in the dust, there is also the undeniable fact that he is doing exceptionally well in Kalos. His current team of Pokemon are very well trained and he has three rivals that have and will be helping him grow as a trainer. Let's not forget his vow to Diantha, who will no doubt be present at the Kalos League, to win the League and have a rematch against her.
We also have to consider the fact that even by the end of March, Ash will still not have had his 8th Gym Badge, so it's likely he'll get it during Summer or Fall, which means the League will probably occur at the end of the year or in 2017, leaving a whole 10 months of episodes that could potentially deal with the Elite Four.
tl;dr I think XY is the saga where all three trainers will succeed in their goals. Clemont imo had completed his goal with his battle against Ash for his 5th gym badge. What are your thoughts?