MSN Explorer carries a version number of 6.x, which makes one wonder how much of what we're seeing in the browser will later turn up in Internet Explorer 6.0. The interface offers a definite improvement over the current releases of Internet Explorer, but MSN Explorer skimps on entirely too many features to serve as a complete replacement for Internet Explorer.
It's also clear that some of the changes and interface elements in MSN Explorer were designed at least in part as a response to Netscape 6.0. The sidebar pane with customizable "My Stuff" content is an obvious knock-off of Netscape 6.0's My Sidebar, and the large, eye-catching toolbar and simplified interface design also take cues from Netscape 6.0's layout.
In light of these factors, my guess is that Microsoft will find a way to introduce modified versions of the "My Stuff" sidebar pane and the redesigned MSN Explorer toolbar into future releases of Internet Explorer. I would be very surprised to see the web-based configuration settings used as the default for Internet Explorer 6.0. Similarly, don't expect the MSN Explorer e-mail client or its address book to make the transition to IE 6.