Once killing by Presidential decree was approved for any President, getting that 'tool',  (as President Obama referred to it in this interview) back into Pandora's Box became impossible.  

How much Trump will use it and against which targets is totally unknown, and may never be revealed to anyone but Congressional oversight committees sworn to secrecy.

Obama has been relying on the Bush Iraq war authorization; why should or would  Trump not do the same?

http://www.politifact.com/texas/statements/2014/mar/19/kesha-rogers/four-us-citizens-killed-obama-drone-strikes-3-were/