TokuDB won't release the allocated blocks (it will reorganize its internal blocks to achieve max compression but as far as I know and saw won't release what it has allocated previously, but I might be wrong :) ).
Sooooooooorry, I have to take it back - just saw now that one of my Tokudb shrank from 5'554'252 to 5'423'180 KiB.
Still please don't expect big shrinks with TokuDB when having big variance of active data as it's not its first priority (first prio is to be fast and/or use little space).
Noooooo, please tell me that it's not true - it's the foundation of many of my experiments delivering huge performance and flexibility compared to anything else...!
