Microsoft is issuing the warning since the early 2014. Microsoft will also help in migrating the servers to the latest server OS. Microsoft usually provides mainstream support for 5 years from the launch of its products like Office and Windows. Mainstream support includes updates which adds new features to the OS and improve their performance. When mainstream support ends, Microsoft provides 5 years of extended support which includes important security updates but not new features.
Mainstream support for Windows 7 is ending on January 13, 2015 and extended support on January 14, 2020.