Own voice/diverse stories are at the top of most, if not all of the YA editor's wishlists, so it's trending in terms of publishers want to acquire own voice and diverse stories, but it's not a trend in the same way as paranormal romance and dystopian and some of the others were. It can't be, because stories about diversity can't really be categorized in the same way. You can have a dystopian and a paranormal romance and a sci fi and fantasy and so on and they can all have diverse characters written by own voice authors. So, in that sense, own voice YA is here to stay for the long haul, and what will happen is that editors will (if they haven't already) start to look for new ways to incorporate diversity without diversity being the main selling point of the novel. For example, instead of a story about a teenage boy coming out to his friends and family, they will look for a story about a teenage boy who is gay but whose sexuality is not necessarily a key element to the plot of the story. So, less books like Simon Vs. The Homosapiens Agenda and More Happy Than not, and more books like Romana Blue and I'll Give you the Sun. All amazing books, and 3/4 are some of my personal favorites. But they all incorporate sexuality in different ways, some more head-on than others. Or, perhaps, a better example is Marie Lu's newest endeavor, Warcross. The MC is Asian, female and has rainbow hair. But no one is pitching/selling the story as a diverse book. It's about so much more than the MC's nationality, gender etc. It's a plot-driven book with a gripping concept.
Personally, I think the next big wave/trend is going to involve historical events being retold from diverse perspectives, and re-inventing old stories which have reached public domain. Showing classic stories in a new light so that they are more relatable today. Let's recast characters and have fun with it. Show me a bisexual teenage Peter Pan. A black Alice and Wonderland story. A hispanic Dorothy in Wizard of Oz. A transgender Snow White. We're already starting to see some of this done in both film and literature and it's great. I think YA is as strong as ever. I base that on the fact that so many agents have included YA in what they are open to representing, and that so many publishers now have YA imprints.