This is a whole new Microsoft geared towards cloud services now. IE is part of that platform goal, so it makes sense that they accelerate its development. I can imagine that MIX will include an announcement for a beta for the next set of Expression tools from them, and I'm looking forward to it because Expression Web is one of the best web editors IMO. Also, WebMatrix is just plain awesome, but I don't expect much of it to be updated during MIX because, well, it's free, and the web app dev tools (Visual Web Developer Express, which WebMatrix's editor is based on) don't get updated at the same time as the HTML tools. The pure HTML stuff is updated to the bleeding edge because HTML5 is evolving as you read this. VWD lags behind somewhat because server-side markup (ASP.Net) is updated on a slower schedule to coincide with IIS releases, which rarely happen outside of OS releases. The SharePoint Designer stuff is even further behind, but corporations don't mind one bit.
BTW: Does anybody notice how small some of the new applications are that are coming out of MS? I'm noticing this of IE9, WebMatrix (which includes a version of IIS), MSE, etc.
Also, when is this form going to get fixed for IE9??