The mudbox thing is in the works, theres an article with one of the original Skymatter developers in 3d world. He now works for Autodesk as a tech adviser or something.

He's only really hinted of a 'mudbox' style module being incorporated into Maya but as far as Mudbox goes its still going to be sold as a standalone package and the next version will have more features available to enable you to produce a more finished model, in a nutshell it sounds like texturing and all that stuff will be heading in its direction putting it on a more competitive level with Zb.

Chin Chin
_J