GSC felt like you were playing the past in the present-- it was really, really, a wierd feeling. RBY was just, an adventure. Interacting with the world, and seeing cities interacting with Pokémon.
RSE sucked never mind it.
I think by this point, everyone is assuming DP is going to be about the future, and like in GSC, playing that time period in the present. There might be some sort of foreshadowing-- you know how in movies that absolutely know there is going to be a sequel, this sometimes allows them to not necessarily tie up all the loose ends in that single instance (re: Star Wars Episode V, one of those LotR movies) I would not be surprised at all if this story ended with a sort of looming incompletion-- not necessarily that the evil Team won, but that evil as a theme beat out good this time, and there'll probably be a lot of foreshadowing with regards to the next generation's occurances in terms of plot.
It won't be SUPER evil, it could be something as simple as the final boss bad guy being defeated, but announcing they will return, leaving us all in eager anticipation of the next series, when we find out what their next plan is. Or they'll be defeated and leave us with some haunting message that even though they're gone, the effects of what they've done is still present in what they've done to Pokémon/people/cities/whatever.
Nah I'm just thinking too much again. I do like my general theme though; the future being lived in the present (opposite of GSC), and a few loose ends not tied up (opposite of FR/LG, whose Fame Checker and Rainbow Islands sought to bridge between Generation I and Generation II).