I don't think we'll see the lighter full size model iPad 5 until later than March, unfortunately. I'm actually really looking forward to the iPad getting the iPad mini/iPhone 5 treatment and will definitely be picking one up. However, I find it odd that people keep saying the 128GB release is proof we won't see the new model in the first half of the year. That doesn't seem to make a whole lot of sense as an argument for a few reasons.
1. Am I wrong in thinking the 128GB model differs from it's lower capacity counterparts very little? Every part is the same except for switching out the flash memory modules for bigger capacity ones, right? Not difficult. I bet the factories weren't shut down for more than an hour while they crated in the bins.
2. They have been making 128GB models for several weeks. Production ramps up on a new product release before the announcement to have as much stock as possible. The 128GB models were probably being made as the initial ramp-up of the iPad 4 (which wasn't that different from making the iPad 3) was being wound down. They replaced a few production lines with the 128gb modules and printed a different number on a box, that's it. The reason you didn't see bigger capacities before wasn't because it was difficult to do, it was because apple's numbers didn't jive yet to do it. They didn't have quite the right profit margin to put the bigger modules in and then medium-gouge, but not outright fleece their customers into a rage the way they do with all capacity upgrades. They want you paying out the nose for more storage, but not out the ears, too. Those numbers worked out recently, it seems.
3. They aren't going to sell that many of the higher capacity. The 64GB models were the lowest selling to begin with. It's awesome they're looking ahead to higher capacity models for truly replacing laptops for some people. It marks a big shift going forward. We will probably see the 16's go away within a couple of refreshes, which is great. But, while the iPad is not a niche product, the iPad as a full laptop replacement with the storage capacity to pull that off definitely is. The price is 8 or 900 dollars. That's not going to fly off the shelves the way a 4 or 500 dollar tablet will. It's for rich people who want to max out their iPad to go with their maxed out computer they don't need, or the tech savvy who are trying to be more mobile and do away with their laptop altogether. The latter of which, by the way, is probably waiting for the iPad 5. There wasn't a line at the apple store for the 128GB iPad capacity. A few nerds walked in, bought one with no trouble, and walked out and put it in a case so they can sell it in 6 months. The rest got them online. That's it. They've probably sold the vast majority of the new capacity that they're going to sell already without much fuss. The people who were clamoring for them have them already or are waiting for the 5.
So, in my opinion, it wasn't a difficult switch to make the 128gb model, they did it quick, then released them, have probably about sold the number they're going to sell, and that's it. It's over. The fact that they just updated the chip last fall and that the 5 is going to have to be completely redone internally cramming enough battery into a casing with very likely new display technology is why we're going to have to wait a little bit for the iPad 5. Again, I am assuming we do have a bit of a wait than March, but not because a bigger number on a box for the laptop ditchers.