As I said, I think we'll get more generic noises before we see a full set of tailored cries for every Pokémon. Scraping of claws against dirt as the Pokémon shuffles around idly. The occasional grunt. A roar as it attacks. Generic chirps from bird Pokémon, et cetera. Sound clips such as these take up very little capacity on today's cartridges, and even less on those of tomorrow. Sooner or later, the Pokémon will make more sounds, though they'll probably keep their current cries (possibly enhanced a little) for quite some time. I mean, in gen. V we had "entry sounds" based on the Pokémon's weight, as it came out of its Poké ball.
Still, it's probably not high on the list of priorities yet. At the moment, having more and more advanced cries for each generation of Pokémon seems to be enough. I really hope Yveltal keeps that roar from the announcement trailer.