There is no technical limit on agility, but at some point there will not be any benefit to adding more, since the maximum chance to hit is 94% and the minimum chance to be hit is 19%. Depending on your character level (and class), 200 may be a little higher than you need to reach these limits.
There are no other limits for stats. A survivor with a constitution of 1000 will get a bonus of 5000 hit points and 300,000 stamina, for example.
See
differences between classes for a just-added example on the maximum effective agility.
