Today I went ahead with the
dissection of Kindle 4 (ruining it in the process). Uncovered:
Battery and power management chip,
ARM Cortex-A8 CPU
128 Megabyte RAM chip (half the capacity of Kindle 3 Keyboard)
San Disk Flash chip
There is also connector next to the CPU that I suspect to be a serial console, however it will be tough one to hook up to. Nothing like K3 plugs - some precise soldering will be needed.
Motherboard is glued in.
Battery is glued in so tight that if you try to pull it out you are likely to destroy it in the process (hint: lithium catches fire when exposed to air). It also has a custom connector so it is clearly not replaceable period.