The anime shifts into BW2 but with the same characters. I believe it's called Adventures in Unova.
The main differences are that Ash and the gang meet up with old Pokemon from other Regions in Eastern Unova. They also replaced the final battle with Drayden with Roxie, the Poison Gym Leader.
Near the end of the series, we meet a journalist who uses Pokemon from the Kalos region (namely Gogoat, Heloptile and Noivern), who introduces us to Kalos Pokemon. (SPOILERS) Ash, Cilian and Iris part ways, each chasing their dream, with Ash leaving for Kalos with the journalist.