Mine typically plateaus around 3.4GB, though instead of memory usage I'm just crashing.
EDIT: After doing some research, it looks like Warframe is susceptible to memory leaks on PC. I have a program failure as a result of memory leak which falls under "RADAR_PRE_LEAK_64" for Windows' error codes. I personally don't know the extent of the leak and how far it'll go but I'm getting failures with 32GB of memory.
A memory leak stems from a program misusing its memory allocation by not properly freeing up memory when it is no longer in use. An example of this is a program needing to store data in the RAM, the system allocates memory for that task, the program finishes its task but does not free up the memory that was allocated to it.
