The scripts for creating a Debian package of Kibana 4 was merged months ago. Any reason tarballs are still the only thing published on elastic.co?
Sorry that I can't give you an answer but I'm wondering this myself. Elasticsearch and Logstash both have debian packages while Kibana 4 only has Windows zip, Linux tar and so on.
I've asked the team to share what's happening here.
We're all pretty busy putting awesome features into the releases that sometimes stuff like this misses out. But we know this is important!