ARM controllers like this Cortex-M3 come in a range with flash capacity going from 8 to 512 KiB and up. TCP/IP stacks in embedded go from ~7KiB for uIP to 256KiB compiled depending on strictness/flexibility of implementation. The controllers can probably upgrade to IPv6 because of the nature of wireless firmware upgrades in embedded systems. The firmware is spread over different packets, so to assure a successful firmware download it's always written to a reserved region of progmem and checked before doing the actual code upgrade. If they did their homework they have flash space that is (2 + margin)*code size. My bet's on yes, it'll upgrade to IPv6.