You have hit the nail on the head.
I work for a small company where we recently considered moving to Linux on our workstations. The Operating System was not an issue, but the cost of retraining our staff to use OpenOffice out-weighed any benefit we might gain. Taking even half a day to train a busy executive would cost the company more in lost time and productivity than we could ever hope to gain in savings through licencing costs.
Meanwhile at home I have switched to OSX without any drop in productivity (well apart from time wasted playing with all the pretty widgets) because I can use Word with no time spent relearning the system. Someday I will try iWork but I am just too busy right now.
Microsoft may create a version of Office for Linux, but it will be after they have lost the battle for the desktop not before.
Disclaimer: "These opinions are my own, though for a small fee they be yours too." -- Dave Haynie