In chemistry and many branches of engineering, Word already is more popular than LaTeX.
In mathematics, and most branches of physics, LaTeX is much more popular than Word, and with very good reason. I have no idea of what the proposed changes are for Word 2010, but I somehow doubt that the current painful way of using the equation editor is likely to be very attractive to these practitioners. LaTeX's superior fontwork also is a major advantage that Word currently cannot match.
The third issue is platform independence. Though versions of Word exist for Mac, Pages has come along very rapidly in the last 2-3 years, and will likely fragment the Mac market. Mac and Linux are both gaining market share (usually at the expense of Windows, and especially in academic settings), so unless Word addresses problems with the WYSIWYG method of entering equations (maybe steal some ideas from TeXMacs), and makes a concerted push on these two platforms (its non-existent on Linux), I do not see how it can make a dent in the traditional strongholds of LaTeX.
Most journals do not accept MS 2007 submissions (even the Word friendly publishing houses), let alone MS 2010.