Most of the community expected Windows 10 to be released fall 2015, however Microsoft made a announcement on their blog that it will be released summer 2015 instead. There isn’t a date set in stone yet but months sooner than expected is welcomed!
Windows 10 will be a free upgrade for Windows 7 & 8 users for the first year as Microsoft introduces their subscription based plan. There hasn’t been a price set by Microsoft for this subscription plan yet.
Read the announcement blog post here: http://blogs.microsoft.com/blog/2015/03/17/windows-10-launches-this-summer-in-190-countries-around-the-world/