During a keynote at the Intel Developer Forum, Microsoft Corporation executive vice president of marketing Tami Reller said that the Windows 8.1 RTM build was downloaded over 2 million times in 24 hours. The pre-release build was released for developers on MSDN and TechNet. The public release is happening on October 18th.
Back in August, Microsoft said that the Windows 8.1 RTM build was completed. Initially Microsoft said that they were not going to release it on TechNet and MSDN until the general public gets it, but they were heavily criticized for that.
Microsoft released the build 3 days ago to developers after getting feedback from the developers.