I've updated jPlayer on a site and it seems to work fine with limited testing.
There were a few changes I made to the skins but they really weren't necessary. I've packaged it all up so it's easy to install on your site. No script changes were necessary, just a couple file name and location changes.
Simply download this zip file and place its contents in your mojoPortal installation. Next, add the following to your user.config so mojo knows to use the new version.
<add key="JPlayerBasePath" value="~/ClientScript/jplayer-2-9-2/" />
Hope this helps,