Today at MIX11 conference in Las Vegas, Microsoft announced a new, tenth version of Internet Explorer.Dean Hachamovitch said in his speech: “The only native HTML5 experience on the web today – for Windows 7 with Internet Explorer 9. With it the sites can use the power of modern hardware and modern operating system, providing what was impossible a year ago. Internet Explorer 10 will make borders more widely available to developers. ”
Release date was not called, but now preview version  is availiable to download. It is reported that it compared with IE9 added support for CSS3-gradients for background images.
It is unknown whether this move means that Microsoft decided to completely switch to a strategy of frequent new versions, which Google Chrome (and, more recently, Mozilla Firefox) follow.
More details official text at microsoft.com