No Doubt
I'm sure that at least one third party vendor has a compact external battery ready to go. Also, while Apple's stated $129 battery replacement seems reasonable enough (I have paid more than that for an extra laptop battery), I'm sure that by the time that people are actually to the point of needing a replacement, there will be third party vendors like those for the iPod that will do the replacement less expensively, or with higher capacity batteries.
I wonder if there's a market for an 'extender' battery pack for the MBA (or other Macbooks) - similar to those available for the iPod.
I'm sure that at least one third party vendor has a compact external battery ready to go. Also, while Apple's stated $129 battery replacement seems reasonable enough (I have paid more than that for an extra laptop battery), I'm sure that by the time that people are actually to the point of needing a replacement, there will be third party vendors like those for the iPod that will do the replacement less expensively, or with higher capacity batteries.