I do not think the iPad cameras will ever be considered more than a nice extra. The screen size is great, but the iPad is too big to effectively handle in a lot of photography. The retina screen will mean some adjustments, but should not be a major inconvenience. I have a 32 Gb model now. In making my decision of what size to get, I looked at my usage graph. I have 6 Gb in apps, the same in music, and over 12 Gb free. So even if my apps double in size, I will still have a healthy reserve. And about half of my apps are rarely used, so they can be taken off the iPad. If they become desired in the future, I can always download them from my computer.
Good point, Seadog! If you want top quality photos, buy a top quality camera. The iPad camera is what it is - average.