I'm not exactly sure what you mean by backward-compatible in this context. We introduced ability to export and re-import Kibana 4 charts in Kibana 4.1. Given that 4.1.1 is a bugfix release, charts exported from that release should be compatible with Kibana 4.1. You cannot import them into 4.0, since that version doesn't have import functionality, and you can't import them into Kibana 3, since that version uses a completely different dashboard schema.
Product compatibility information can be found here: https://www.elastic.co/subscriptions/matrix
Kibana 4.0.x and 4.1.x are compatible with Elasticsearch 1.4.4+