An eager hacker over at MobileRead has ripped open his Kindle Oasis, and revealed that it has a 245 mAh battery, runs on a Freescale CPU, and uses Samsung flash storage.
There's no wireless chip visible, but based on the design of the Echo there will be a discrete wireless chip, and it will be on the backside of the board. So we'll have to wait for a more complete teardown before we know which chip it is using.
Since I did not want to wait for somebody tearing down the Kindle Oasis anymore I decided to open up mine. The shell uses double sided tape to fix the cover to the back so one cannot take apart the Oasis too often without replacing it. otherwise the disassembly is fairly easy but be aware that the plastic noses that hold the cover attached towards the thicker part of the case are not really angled correctly for being detached damage-free too often.
No serial port pins seem to stand out but there are quite a few testpoints that have a voltage between 2.5v and 1.6v fitting an active serial pin.
I could figure out a few of the pins on the backcover connector. the left and rightmost pins are GND and case-ground and the second leftmost carries VBat the two remaining pins seem to be a i2c bus for the cover.
They also posted this photo of the Oasis innards. Do you see anything interesting?