Hi 
There seems to be an assumption that MS Office would be un-installed or that
people would be forced to stop using MS Office and that the change would have to
be implemented 'overnight'. None of that assumption is valid.
Agreed, it would be a gradual change, but it would change. Having two office suites installed means more work for IT support for the program and it's features, plus supporting the interchange of files. And, you will always have those users who will not make a voluntary switch from old to new until forced, causing continuing difficulty is sharing files. I'm not IT, but been there done that when the switch was made from WordPerfect (the better program IMO) to MS Word.
People could and probably would continue to use MS Office but would gain access
to the extra functionality offered in LibreOffice. This is much the same as
Adobe Acrobat Writer which office workers are often expected to install or
upgrade in order to read pdf.
Pdf is dominant on websites as THE way that documents are available for
download. Often there is a download link nearby in case anyone has not got the
latest version. People seem to consider it completely normal to have to
download and update Acrobat but it doesn't stop them using MS Office.
I suspect no one considers having a special program to read PDF's as being "strange" is because only recently have office suites started to be able to read and create PDF files.
I haven't used MS Office for a long time now, but if memory serves, 2003 can't do anything with them, 2007 can only create. I don't know about 2010.
I've not done any kind of comparison, but I'd bet no office suite can match the features of Adobe Reader 9. And I'd bet 10 has even more features. So, until the office suites can "meet or exceed" Reader's abilities to work with PDF files, there's going to be a separate program to read and manipulate them, plus Acrobat or similar to create them.
Ken