Elasticsearch 2.x has removed support for two properties being utilized in the logstash template:. The geoip property sets "path" which has been removed. The tags property sets "index_name" which was removed in the same patch. On a quick overview it seems we can drop these two values, not sure how necessary they were in the first place. ES 2.x still supports reading indices with these values set, so there is no problem with migrating. ES 2.x does not support creating indices with these values though so the templates need to be changed before an upgrade occurs.
There is no migration path for dashboards from kibana 3 to kibana 4, which is also being done, so it's not likely worthwhile to review existing dashboards for potential breaks.