Pokemon Bank and Poke Transporter coming end of December
If you ever felt like the PCs in Pokemon games never really held enough of your Pokemon, you can rest easy with the new Pokemon Bank, which will hold up to 3000 Pokemon at once. Holy crap, that's... a lot!
But how do you get all the Pokemon there? That's where the Poke Transporter comes in. With this app, you'll be able to transfer Pokemon from older games like Pokemon Black and White or Black 2 and White 2.
The Pokemon Bank service will start out with a free month trial and then cost a mere 4$ a year to keep your account running. If however all you want is to transfer over older-gen Pokemon to Pokemon X and Y, you can probably get away with simply using that free month to transfer everything over and then being completely set.
You can check out this video which gives a pretty good overview of the service. It's neat, but I don't ever see myself needing storage for that many Pokemon.