As part of today's Pokémon Direct broadcast, we learned all about the Pokémon Bank Service, which will include a yearly fee to store up to 3000 'mon in the cloud. That has obvious benefits for Pokémon X & Y, but will also likely be used in future releases and, in the case of Poké Transporter, with the last generation of games and hardware.
Poké Transporter is an app that'll work in conjunction with the Pokémon Bank. If you have a cartridge copy of any of the Pokémon Black and White or Pokémon Black and White 2 games, you'll be able to upload your 'mon to the Bank and transfer them from there into Pokémon X & Y; it seems to be an ideal way to carry across your hard work from the previous games into the new generation for the franchise.
While the Bank will have a yearly fee (it'll be 500 Yen — about $5 — in Japan) it may be possible to utilise this without signing up fully, as a free trial period will be available. If the Poké Transporter is available on day one it may be possible to complete the transfers for free, and perhaps Nintendo will be happy for that to serve as positive marketing if gamers can see the Bank's uses and features in this way; we'll find out soon enough.
Are you planning to bring across your Black and White 1 & 2 collections to X & Y?