Microsoft Has probably a trial in mid-March.
It has been fairly quiet around the next version of Internet Explorer since Microsoft revealed a very early release under the Professional Developer Conference (PDC) in November last year. 
The closest you could call a news since that time, Microsoft's relatively recent involvement in the working group of W3C's vector graphics standard, SVG. This participation may indicate that the company has plans to support the standard, at least in the long term.
Now it is however clear that the head of Microsoft's IE team, Dean Hachamovitch, will reveal more IE9 News at MIX conference held in Las Vegas in mid-March.
According to this post will Hachamovitch talk about changes and improvements have been made since the PDC, and it promised that his presentation will include several surprises.
What this goes on, one can only speculate, because it would not be surprising that IE9 is far faster and has much better support for web standards than IE8. There will also be very surprising if not Microsoft take this opportunity to release a public test version of the upcoming browser under the MIX conference.
Previously, Microsoft released new versions of Internet Explorer rather close to releases of new Windows versions. IE6 came around the same time as Windows XP, IE7 came a few weeks before Windows Vista, while IE8 was about half a year before Windows 7 If Microsoft sticks to their plans to release a Windows version with about three years between, would a continuation of the aforementioned trends have led to a release of IE9 late in 2011 or in 2012.
It seems unlikely that Microsoft will wait as long this time.
Microsoft will also tell you more about the Mobile version of Internet Explorer included with Windows Phone OS 7, at MIX. It will surprise a lot of this is far more modern than IE version that was introduced with Windows Mobile 6.5. Certainly, this current IE Mobile edition a great improvement over its predecessor, but it is nevertheless a fact that IE6 engine, as the current IE Mobile is based, is very old.
