Yes, it's long past the time to switch to liquid cooling. Meeting current emissions standards with an air cooled engine requires too many compromises. I've heard horror stories about rear cylinder heat from late model air cooled V-twins.

As for engine heat, GL1800s handle it better than any bike I've owned. The side radiators do a great job of directing much of the heat away from the rider. With the big front radiator on my Valkyries most of the heat gets dumped on me.