This will be supported once ZOOKEEPER-107 feature is in. With this users will be able to dynamically add/remove the zookeeper quorum peer(s).
I hope the following jira link will help you to get more idea.
https://issues.apache.org/jira/browse/ZOOKEEPER-107 : Allow dynamic changes to server cluster membership
From: Pramod Srinivasan [[EMAIL PROTECTED]]
Sent: Wednesday, February 20, 2013 4:34 AM
To: [EMAIL PROTECTED]
Subject: quorum size
I have an application where the quorum size for zookeeper server should change dynamically, can this be done at run time?