Besides movies, two other areas that now occupy 2nd and third priority on my smart phone SD card memory are audible books and GPS downloaded maps. I can see both of these possibly consuming space on my ipad too. While I feel my video editing skills demand more robust editing capacity of a strong PC environment, I can see imovie, garage band and iphoto being real hogs on the ipad in the near future for many. What all this means is, if you have no plans to do any of this stuff, use your ipad maybe 2-3 times a week, I still say 16Bg will be fine. But if any of these storage requirements are in your future, Better spring for the $200 and get the 64Gb or more storage will probably be on top of your 2013 agenda for upgrade.
I think there is only one additional feature on my agenda for upgrade from the ipad3 and that would be a 3D auto stereo screen. Considering 95% of my video production these days is 3D, being able to play those creations on the ipad is high on my list and would get me to buy again next year.