About the Pokemon Bank

[Excalibur0126]

If your trial pass or annual pass expires and you do not purchase a new pass, you can still withdraw your Pokémon from Pokémon Bank for a set period of time. However, once that set period of time ends, any Pokémon remaining in your Pokémon Bank Boxes will be lost. Be sure to withdraw your deposited Pokémon as soon as possible, or purchase a new annual pass.

Reference: http://www.pokemonbank.com/en-us/faq/