You're not missing a column as such.... what you'll notice if you turn the launcher into portrait mode that there simply isn't enough space to show those extra 'columns.
Still... thinking about the lack of settings in normal Google launchers on previous versions of Android, I wouldn't get too excited that you'll be able to change the number of columns/rows.
I'm fairly optimistic that when the Honeycomb source is finally released someone will be able to mod the launcher code and get a few more settings in there.
Nexus 4 - CM10.1 Nightlies (own builds)
Galaxy S III - CM10.1 Nightlies
Galaxy S II, Galaxy S, Desire S, Nexus One, Transformer TF101