I believe within five years ALL Mac notebooks will model the current MBA. If Apple can definitely squash the demand for BluRay, no optical drive will be necessary ever again. Anything that is too big for download will be sold on flash drives that connect via USB or LightPeak (eventually). It really makes no sense to sell big packages with disks in them anyways... I figure other software makers will start this transition soon, and within five years nothing will be on a disk except BluRay video. Apple certainly wants to remove optical drives, but right now professionals are reluctant.
I think a larger display MBA is already in demand. Also, when actually considering the footprint of the MBA, it doesn't take much more space to fit a 14" to 15" display. Remove the bezel completely, and we're set. A 3.5lb 14"+ MBA would sell. Consumers and non-graphics professionals want 15" of viewable space too. We definitely want more screen real estate.
Honestly, right now I would be completely happy with a 14" display in the same MBA with a 1600x900 resolution. I want that really bad, and I wish I had a direct red phone to Jobs himself to make our case for it!
I do think the next MBA and MBP will have HD display options.
Bottom line, your 15" MBA isn't too far off even if it's not called an MBA.