EPUB 3.1 is the current version of the EPUB standard. It is an update to EPUB 3.0.1.
EPUB 3.1 was developed pursuant to a charter approved by the IDPF Membership in July, 2015, and approved by the IDPF membership as a final Recommended Specification effective January 5, 2017. Changes between EPUB 3.1 and EPUB 3.0.1 are documented here.
The EPUB 3.1 specification is developed by the IDPF EPUB Working Group, consisting of IDPF member representatives and Invited Experts. All Working Group activities are conducted in an "open source" manner: the EPUB 3 Working Group project site is publicly accessible and contains a source code repository for specification and related work products.
All comments on EPUB 3 specifications should be submitted via the EPUB 3 Working Group Issue Tracker, hosted on GitHub. NOTE: you must login via a GitHub Account in order to submit an issue.