No reason in the world that they couldn't develop a water cooled 45° V-twin with a common crankpin. And it's the angle and common crankpin that determines that "sound" so many of you seem to think is so important, not the method of cooling. The V-Rod sounds different because the V angle is different, not because it has water jackets and a radiator. And btw, on the subject of sound, if they had water cooling they could run tighter clearances and the water jackets would insulate some of the excessive mechanical noise that causes Harley to run such quiet mufflers to meet overall noise emission standards. Quiet the mechanicals and you can open up the exhaust.
There will come a time when the current formula of just increasing displacement to maintain the anemic performance levels will come to an end. The current design can only accomodate so much bore and stroke, and it's getting pretty close to the max. Right now, they are just treading water (pun intended) but they will eventually have to sink or swim. I'm still waiting to see if current management has the balls to make the tough choices, or if they just maintain the status quo, take the money, and run.
Jerry