No, Internet Explorer 12 has not been released -- yet. This is about Internet Explorer 11 on the Windows 10 Technical Preview. While it’s not a brand new Internet Explorer, Microsoft has still bundled in some brand new performance improvements.
The first is support for the new HTTP/2 protocol. This is a prototype of a revision to the HTTP/1.1 protocol which is more than 15 years old. HTTP/2 is an ongoing project trying to improve performance on end-user perceived latency, network, and server resource usage through multiplexing, header compression, and Server Push.
Third, Internet Explorer on the Technical Preview will be parsing domains using Mozilla's Public Suffix List. This came as a surprise to me personally, but it makes me hopeful of continued collaboration that makes the web a more universal place.
Lastly, Microsoft has launched the 'IE Platform Suggestions Box' on the UserVoice platform for users to provide more feedback. This will ensure that Microsoft prioritizes their work on Internet Explorer inline with what the community wants.
If you want to try out the 'new' Internet Explorer, enroll in the Windows Insider Program to install the Windows 10 Technical Preview.