Can Terminators Assault Through a Gate of Infinity?
Gate of Infinity allows units to be placed as per the Deep Strike rules.  According to the Deep Strike rules you cannot assault the same turn you arrive via Deep Strike.  You are also subject to any other rules related to Deep Strike.  You scatter, are affected by terrain, and can mishap the same as if you arrived via normal Deep Strike.

Here's an example forum thread where the general consensus is that you can't assault through a Gate of Infinity.