Sixth generation, Pokemon X and Y, the first series coming to the 3Ds.
Dialga and Palkia are unobtainable in Black 2 (or any other game in Generation 5 (BW, BW2))
Darkrai cannot be found in Black 2. (Or Any of the BW, BW2 games). You need to either transfer from a previous generation that has Darkrai or ask a friend.
The current generation is VI or six with the release of Pokemon X and Y.
Both Colress and Ghetsis are villains in Pokemon Black 2 and White 2.
You cannot get Regigas in Pokemon Sapphire as it is from the next generation of Pokemon
Did you mean the next game? In that case it's Pokemon White/Black which introduce the 5th generation.
in about 3-9 months
No, he doesn't start evolving until the next generation of pokemon.
The 'next' Pokemon game was Pokemon Mystery Dungeon: Magnagate and the Infinite Labyrinth. The next main-series game will be Pokemon X and Pokemon Y, the first 6th generation games.
To face Thundurus in BW2 is impossible as you can only get it through trading with White.
Most of the time its spiritomb because in bw2 she 1st sends ou that pokemon
aipom's evole is a Pokemon from the next generation after emerald so its impossible to receive him.