I think it all boils down to what exactly you plan to do on your iPad. Do you really need the biggest, slimmest, best iPad sold in the market right now?
Years ago, I bought the iPad2 on impulse. While the whole world seemed to be queuing for it, I had the chance to buy one off the shelf with no queue, no people, no hassle. Big regret, because I barely had any use for the damn thing. Yes, the occasional Skype, and some games, but as a device the surf the internet, I prefer to sit in front of a PC.
Recently, I sold my iPad2 and bought an iPad Mini instead. For me, the form factor was good -- easy to lug along, great screen (I showcase my pics via iPad occasionally), and it does everything else decently. I've even gone one step further by purchasing some digital mags so that I can read (something I'd never considered with my iPad2 -- too heavy!). Wifi reception isn't as good as my iPad2 or my iPhone, but it is bearable in most scenarios.
So I guess my answer is... do you really need an iPad 4?