My guesses (hopes!) based on some discussions with a client who's going to MIX07 next week

- Some sort of competition to Amazon S3 hosting but with ability to upload .Net applications as well as data
 
- The ability to write C# instead of JavaScript across browsers/sidebar gadgets etc  (I don't mean Nikhil's C# to JavaScript conversion library - I mean actually running the CLR, which is sort of what Larsenal said)