I think when ever some new person enters an activity, there are two basic questions they ask: Can I do this? (do I have the strength and ability) and Can I afford this?
That is why the H16 class thrives. More people can afford it and do it.
The further you move away from the H16 class, up the pyramid of cost and complexity, the fewer sailors are able to both afford it and "do" it. When you get to the top of the pyramid, (the Tornado class for example) there are very few sailors who have both the money and ability to be sucessful racing it. The rapid growth of the F18 is due to it being somewhere in the middle, between the H16 and Tornado. And more numbers attract more sailors to the class. To a man, each one of the Florida Inter 20 sailors who are now racing F18's say the same thing: "I like the Inter 20 better as a boat but the F18 has more boats at the regattas." They would rather sail in a larger fleet than on a faster boat. Therefore I do not see any hope for an "Ultimate 20 footer" (costing what, $20-30K?) making any signifigant dent in the F18 market. I won't have an F18 for one reason, I sail alone alot more than with crew.
I still love the spinnaker and the A cats are just too much money for me. Therefore, in my case, the F16 makes perfect sense, but that's just me. Thank God we are not all the same! I don't think I could stand bumping into -me- all day!