(chuckling alertly) Funny you should mention Serena. Suffice to say that I'm certain that you weren't the only one with a dropped jaw at the explosion of activity there. My overarching scenario for ending Pokémon in Unova could surprise you even further, further still the convergence that happened a little over two years ago and ended up driving said scenario. As a possible taste, Ash and Dawn make an appearance to stop Teams Rocket and Plasma from basically wiping that region out... and Cilan, Iris, Nate, and Rosa are the ones focusing on freeing Kyurem from Ghetsis' psychopathic plan, which involved obliterating the Skyarrow Bridge and attacking the Driftveil Gym, among other objectives, as I recall. In Serena's case, she'll have had a reason to know Ash before he even became a Pokémon trainer, and here he is, exploring the world with a girl who'll have helped him take down one or two cult(s) of world-ending terrorists and this franchise's most notorious criminal group, seeing the leaders of the last two groups die in the process. You might not have to guess how shocked -- and heartbroken -- Serena could be once she realizes just how far Ash and Dawn have progressed by the end of my scenario.