I think some people missed the 'reasonable' part of the title.
Apple will not be making the screen smaller. They decided on 13.3" to keep it usable for the majority of buyers.
Apple will not be adding esata, firewire (a dead standard unfortunately), ethernet or anything like that. The design concept behind the MBA is 'wireless'. Note the 'Air' in the name.
Apple will not be making the battery removable. Get over it.
Apple will not be changing the tapered design of the MBA's case. It is an intentional way of making the MBA look even more thin then it is.
We might see an additional USB port as a nod to those users who really need it, but I doubt it. As Intel finalizes the wireless USB standard I think that will be the way the MBA heads.
We may see an option for a larger amount of preinstalled RAM. I think it is an even money bet that they will keep it at 2gb though. 2gb is more then enough for most consumers.
We may see an integrated HSPA modem and SIM card slot. I think that the lack of a WWAN option was a glaring fault in the original MBA. Now that Apple has partnerships with carriers in over 70 countries for the launch of the 3g iPhone I think it is a perfect time for Apple's ultraportable to get some 3g love.
Apple will definitely be using Intel's newer 45nm processors. They will be cooler and faster then the current ones while using less power and allowing a longer battery life. They will definitely move to a SATA HDD and SSD due to the simple fact that there arnt many new PATA drives being made. This will allow larger and faster drive options.
My personal belief is that we will see the newer 45nm Intel processors, larger faster drive options and integrated HSPA. That is it. Anything else is wishful thinking.
If your needs include a plethora of ports, lots of speed and storage or removable batteries then you should not be considering the Air. Apple has very clearly segmented their laptop offerings, there is never going to be a Macbook Air Pro.
Excellent post. I completely agree. Apple isnt going to make any significant changes. just like the new iphone 3g, it doesn't have many new changes but still many people will sell their old iphones to buy the new latest and greatest.