I think everyone here is pretty much betting on the protagonists to follow the whole X and Y theme we have going. However, the default names of the protagonists haven't seem to fit the theme of the games since Gold/Silver/Crystal, where the characters were pretty much named after the titles.
May and Brenden don't fit with the Land and Sea theme for RSE, except for their optional default names (i.e. Landon/Sean or Terra/Marina).
Dawn and Lucas, other than sharing a common meaning of origin ("light"), doesn't seem to exactly fit with the theme of space and time like Diamond and Pearl did. Nor did they really reflect the title of the games. Unless you really wanted to get technical with the gems and their correlation with light.
Later in HG/SS, Gold (or Silver if you played Silver) had his name changed to Ethan while Kris was replaced with Lyra. Their common meaning related to sound, which could more or less go with the importance of bells in the games, but one could say that's really reaching if you're bent on finding a connection between the protagonists' names and the theme or title of the games.
In Black and White we got Hilbert and Hilda (Oh my gosh GameFreak, what were you guys thinking!?), but the origin of those names basically mean to fight or to battle. That could pretty much fit for any Pokémon game honestly and it didn't share a connection to the game titles or the theme of the story.
Finally we got Rosa and Nate for Black 2 and White 2. A huge improvement over Hilbert and Hilda if you ask me. But again, their connection lies within the word "resonate." The only close similarity I see with those names and the idea of B2W2 is that the games were sequels and it was completing or filling in the pieces of what Black and White left open. Even that could come off as reaching.
My point is, I don't think the names are going to start with an X or a Y and they may not even relate to the theme of the games. Their names may be more likely to share a commonality between each other (and maybe be of French influence) than share a link with the games themselves.
I think that's what we should be looking for.