Whether Yveltal becomes Uber or not is a different story, but I can see this Pokemon having a lot of potential (even top tier). There's a lot to be said about Yveltal that a single skimthrough won't tell you. First of all - it's typing. I think some people underestimate it, but imo it's an extremely powerful typing. On the offense, it's top tier typing with only 6 possible type comboes resisting it, and less that possess them (and even less that are actually tanky enough to withstand Yveltal). This, combined with a decent number of Pokemon in Ubers weak to Dark, really gives Yveltal an edge. Oh and there's Dark Aura, which as far as I've calculated in numerous Vs. Yveltal vids on youtube (lol I had nothing better to do), is approximately a 30% boost, which grants Yveltal some driving force behind its Dark-type assaults. On the defense, Dark/Flying brings interesting perks such as immunity to Psystrike/neutrality to Aura Sphere, resistance to Ghost (means so much more now with Steels losing their resistance to Ghost, and there aren't many good Normals in Ubers), and immunity to Spikes/Toxic Spikes. Lacking a weakness to Dragon is also a big plus to defensive Pokemon, and Yveltal certainly has the bulk to pull a defensive set off. Its weaknesses are honestly not too problematic, because unless the move is STABed Yveltal can probably shrug it off (SpDef Yveltal takes 50% max from Mega Mewtwo Y Ice Beam). Yveltal's movepool is also quite interesting. It's relatively small, but when you combine that with everything it has, Yveltal can pull off numerous sets with different outcomes. Not many other Pokemon has a movepool as concise as Yveltal's, while remaining unpredictable. Kyogre is probably the closest I can think of. The other thing that strikes me as interesting is that Yveltal does not need to invest in offense to deal respectable damage (Foul Play), but also does not need to invest in defenses due to its powerful Sucker Punch (strongest priority in the game, might I add?), and sustain from Oblivion Wing. This fact can make Yveltal a deceptive threat. I ran some calcs yesterday regarding its offensive and defensive potential but I'm too lazy to find them. I'll tell you this though - Don't set up your mega Lucario in front of a Foul Play Yveltal - it can potentially OHKO you.