While perusing the FCC website this morning, looking for signs of Pika and Alyssum, I happened across an old filing for the Kobo Aura H2O. Kobo launched this ereader last September, and even though it shipped in October we still haven't taken the time to look inside.
The photos don't tell us much that we don't already know, but they do reveal that the Aura H2O has an internal microSD card slot. This tells us that a sufficiently industrious hacker can crack open their device and upgrade the internal storage.
That's not something you can do with most ereaders or even all Kobo devices; like most consumer electronics most ereaders have the internal storage soldered to the circuit board.
And this is probably something you don't want to do with the Aura H2O; cracking the case would both void the warranty as well as break the waterproofing feature.
But it is nice to know that users have the option.