Actually, the Apple distinguishes its Macs as MacBook Air (Late 2011) or Mac Mini (Early 2010). So to claim iPad # makes them seem old doesn't make sense since most people don't know what year the iPhone 2 came out, but they do know that the iPhone 4 is "newer".
Personally, I prefer the number system. Its easy to understand, its sequential and its not pretentious. Calling it iPad HD and eliminating the numbers will only result in more complicated search/product terms in the long run because we'll have to start adding the year in order to properly reference it. And reselling an iPad HD (Early 2012) will be much harder to resell than an iPad 4.
Do you go into the Apple store and buy a Macbook Pro early 2012? No, you buy a Macbook Pro. If we're getting technical, it's the Macbook Pro 8,1 or something like that...