This is not as simple as suggested, state merging is largely an application responsibility. I have a JIRA issue (http://jira.jboss.com/jira/browse/JBCACHE-8) which tackles this, but it will come down to policy-based state merging. So we call the application, which then needs to handle the state merge. JGroups merges the partitioned subgroups back into a single group, but state merging cannot be done by JGroups because we don't know your state.
What you suggested will probably *one* merge policy that JBossCache ships with, but there will be are others, and application programmers concerned about partitions/merging will be able to provide their own policies.
Thanks a lot for your prompt answer !
I guess we will handle this case at the application level then :)
PS: TreeCache and jgroups are really great products !