Disassembly of the device revealed that users will be able to replace the RAM with SO-DIMM modules, although access to them will be limited due to their location under a large heatsink. It is not known for sure whether there are one or two RAM modules, but the memory is not soldered to the board. The SSD is also not soldered and can be replaced: the standard 2230 M.2 can be replaced with a full-size 2280.
What cannot be replaced is the GPU — an AMD RDNA 3 with 28 compute units up to 2.45 GHz and 8 GB of GDDR6 VRAM. The video memory limitation may become a problem in future AAA games, especially considering that the device is positioned as 4K 60FPS with FSR 3. Most likely, the Steam Machine will heavily rely on FSR 3 upscaling, and the original resolution remains unknown, which may affect image clarity.
Until benchmarks appear, all of this remains an assumption. What is certain is that the GPU cannot be replaced — owners can only add RAM and SSD.