Cassiopeia stack limit increase?

On the pbe forums, someone mentioned that Cassiopeia's stack limit was increased from 400 to 500. Given the fact that she only gains stacks now by poisoning enemy champions and passively gaining a stack every 6 seconds, wouldn't the number of stacks required to reach her "hyper-carry" potential have to be decreased to about 300? (She no longer get stacks from last hitting poisoned units and casting twin fangs on enemy champions).

Link to pbe thread:

http://boards.pbe.leagueoflegends.com/en/c/champions-gameplay-feedback/lAHAktOJ-on-cassiopeia