As discussed here: http://moodle.org/mod/forum/discuss.php?d=92548&parent=495344
though there is now a script to convert journal activities to online assignments it is highly probably that many would upgrade without converting which could cause a good deal of confusion and possibly upgrade issues. It would be best if the 2.0 set-up script tested for existence of journals and then prompted user to confirm that user wanted the existing activities converted to assignments before finishing the upgrade.