The Redmond Channel Partner website is my “go-to” source for insight to the Microsoft software roadmaps and software release dates.
Example: The link to the upcoming Microsoft 2016 product suites that are set to be released in the upcoming months.
https://rcpmag.com/Articles/2011/02/01/The-2011-Microsoft-Product-Roadmap.aspx?Page=1
This week, it was announced that SharePoint 2016 RTM will be released on March/2016.