I don't expect HTML5 to crush Flash even for video.
Unless a majority of users move over the HTML5 compatible browsers, it isn't going to work.
Considering how long has IE6 been around despite all of the security vulnerabilities and when you consider that these companies haven't thought these security vulnerabilities as important enough reasons to move their users over to a decent browser, what makes you think that these companies would think the ability to see video on the web being a good enough reason to transfer their users to HTML5 compatible browsers?
If anything, it would discourage employees from using up the bandwidth looking at some random video on the web - all the more reason not to encourage the move to HTML5 browsers.