Sources:
http://www.pcworld.com/article/2873219/windows-10s-new-features-cortana-on-the-pc-continuum-and-more.html
http://www.pcgamer.com/microsoft-windows-10-will-not-be-sold-as-a-subscription/
http://blogs.windows.com/bloggingwindows/2015/01/21/the-next-generation-of-windows-windows-10/
http://www.computerworld.com/article/2825116/free-at-last-after-windows-10-consumers-wont-pay-for-updates-or-upgrades.html
http://www.wsj.com/articles/microsoft-to-show-off-latest-windows-launching-this-year-1421695264
http://www.itpro.co.uk/operating-systems/23119/windows-10-release-date-specs-and-pricing-announced