What can I do after winning the Pokemon league in W2?

Question

I mean,does anything happen to the story(except battling N)?Does Team Plasma have any plans?Do I catch any legendaries?

Answer 1

After you become champion by defeating the Elite 4 in Pokemon W2, you will return to your house in Aspertia City.
From then on, you can :

• Capture/battle Reshiram and Kyurem
  ( Your Rival will tell you to go to Victory road, and
  when you reach a specific spot, a Zoroark will guide
  you to N's Castle. In N's Castle, you will battle N's
  Reshiram. If you win the battle, N will give you the
  light stone. After this, go to the top floor in Dragonspiral
  tower, and there you will be able to battle Reshiram.
  If you catch Reshiram, go to the Giant Chasm, and battle
  Kyurem. After the battle, Kyurem will leave the DNA
  splicers behind. If you put your Reshiram and Kyurem in
  your party, get the DNA splicers from your bag and select
  Kyurem, and than Reshiram from your party to fuse them
  into White Kyurem.)

• Complete the National/Unova Pokedex
  ( When you have completed the Unova pokedex,
  show professer Juniper your progress, and she
  will give you the Oval charm, in which helps
  the daycare man find eggs for you faster.
  When you have completed the National pokedex,
  show professer Juniper your progress, and she
  will give you the Shiny charm, in which makes
  it easier to find shiny Pokemon.
  If you have seen all the Pokemon in the Unova dex,
  show professer Juniper, and she will grant you
  access to the Nature preserve, which has a shiny
  Haxorus living there, as well as other rare Pokemon.)

• Re - battle Terrakion, Virizion, and Cobalion (if you defeated them all)
  (If you defeated all three, go the the original spot
  you fist battled them, and you will have a chance
  to battle them again, but at level 65.)

• Travel to the White forest, Pinwheel forest, Wellspring cave,
  Pokemon daycare, Striaton city, Dreamyard, Accumula town,
  Nuvema town, P2 labroratory, Plasma Frigate, and routes 3, 2, and 1.

• Capture Azelf, Mespirit, Uxie, Latias, and Cresselia
  (you can capture Cresselia by going the the Strange
  House, located by Lentimas town. Once you have
  got there, move items around and meet the spirit of a girl,
  which will give you the lunar wing. After recieving the
  lunar wing, go to marvelous bridge, where you will meet Cresselia.
  You can capture Latias at the dream yard, by going through the
  second gate. *latias will guide you to where it will go)

I hope this helped!

Answer 2

No, Team Plasma basically goes down the drain and doesn't play any major role anymore, though you can battle N, the Shadow Traid and Colress as well as some other trainers like Benga and Alder.

Legendary Pokemon-wise you can go catch Reshiram/Zekrom, Kyurem, Cresselia, the 4 Regis, Latias/Latios, Heatran and the Lake Trio. After catching Kyurem you can also use the DNA Splicers to get Kyurem-B/W, Marrilands has an extensive walkthrough on this

Apart from that you can go around Southern Unova now (You know, the first couple places in B/W which you didn't go to in B/W2 like Nuvema and Accumula town). You also get Black City / White Forest, access to some new Pokemon I believe, and have fun at places like the World Tournament.

Answer 3

there are some thing you can do post game in b&w2.

You'll first need to return to Victory Road, where that Zoroark
blocked your path earlier. Now that you've beaten the game, you can
proceed through into N's Castle, where you can fight N using either
Zekrom L70 (Black 2) or Reshiram L70 (White 2). After beating him,
you'll return Zekrom or Reshiram into either the Light Stone or Dark
Stone, which you can take to its home at the top of Dragonspiral Tower
to have a chance to catch it. Zekrom (Black 2) or Reshiram (White 2)
are at level 70. After catching it, you can return to the Giant
Chasm's cave where Kyurem was to have another chance at fighting it,
except this time, you can actually catch Kyurem. It's at level 70 now,
though. Once you've caught or beaten Kyurem, it will give you the DNA
Splicers key item, which you can use to fuse Kyurem with Zekrom to
create Black Kyurem or Kyurem with Reshiram to turn it into White
Kyurem. You can use the item again to unfuse the two. Apparently you
can't fuse to make both Black Kyurem and White Kyurem at the same
time, though.

how to catch reshiram and kyurem. taken from thissite. here you can read everything about post game. example: catch shiny haxorus, get archen or tirtouga, catch latias o.sv.
team plasma is located at their secret lab at route 17.

hope I helped:)