While I DO get UU is finally constructed, and RU's construction is already underway, here is my most likely to happen theory.
Espeon will drop to UU: Yes, this may seem like a stretch, but XY OU was NOT kind to this thing. The unbanning of two of Deoxys's forms made Espeon face even more competition than it already had. As if Latios, Starmie, and Alakazam, who got a mega, wasn't enough. Also, one word. Aegislash. Its small niche is very hard to notice thanks to Defog's buff, and even then, it still is too frail to use it. However, if Espeon drops to UU, it will find its true home. With a meaty 130 Special Attack, and a new toy in the form of Dazzling Gleam to deal with Dark and Dragon types, Espeon will find its viability home. Being a prime supporter AND Special Attacker, Espeon will turn from facing stiff competition from its fellow psychic types to a monster if it drops to UU. In conclusion, if Espeon does drop to UU, it will be easier to fit onto a team.