I created branch-3.4.0 at commit 4a8221877cc1782b861184f0ccf86238d002af13. Master is now Impala 4.0, and I am updating the version number ( https://gerrit.cloudera.org/#/c/15449/ ).
branch-3.4.0 is not yet a release candidate. There are still a couple outstanding fixes for Impala 3.4. These will be cherrypicked from master to branch-3.4.0 when they land. Thanks, Joe