Thanks to myfixguide we finally have disassembly instructions for Dell XPS 13 9343 2015 model. Before we start, we would like to make it clear that it is impossible to upgrade RAM on it as soldered to the motherboard. So it is best to get Dell XPS 13 9343 2015 with 8GB RAM if you really want to future proof your laptop.
The new Dell XPS 13 has bottom cover made from single block of aluminum that completely seal the components. So in order to access the battery, the SSD and the cooling system, you must remove this bottom panel.
Fortunately it is quite easy to unscrew the screws that hold the bottom panel of Dell XPS 13. Immediately upon its removal, you will find an ultrathin lithium polymer battery with capacity of 52Wh. Attached to the motherboard is the cooling system along with The Intel Core 5th generation processor with Broadwell architecture that does not require passive cooling.
There is one M.2 slot for SSD drive but there are none for memory modules since are soldered on the opposite side of the motherboard. This means only components like M.2 SSD and WiFi modules can be upgraded in future.