I noticed that the Dynamics AX 2012 Systems Requirements document was updated recently, August 2014 at the time of this post.
And min RAM has been updated to 2GB min and 4GB recommended. This is something you want to take note of for sizing your environment especially if you are looking at RDP or Citrix servers for running multiple users. Keep in mind that AX client will only use the memory on the machine based on what the users is doing so some users might not need this other that are more power users might use more that this.
As a recommendation before you rush out and buy equipment you want to factor in some monitoring of the memory usage of a mix of users to determine what is the right level for your environment. You can do simply by defining some typical process scenarios that your users would typically run in a average day. Then turn on some system monitoring tools like windows performance monitor and run the processes and monitor the CPU and memory on the client side. This will give you an better indication of the amount of memory you might need for your environment if 2GB is good enough to too little.