Microsoft has announced the timeline for the release of Exchange 2016, according to which there will be a public beta as early as the summer. The RTM version is then announced for winter 2015:
Initial information has also been published on what is required to use the new "Document Collaboration" feature. According to this, in addition to Exchange 2016, SharePoint 2016 and Office Web Apps Server 2016 are also required. It can therefore be assumed that these versions will be released close together.
