[Zaebal]

This word khalifa is used in sense of "Mazoon",that is the person who has permission to spread the teachings to others,that is why many people prefer the word "majaz" rather than Khalifa.Having said that i find nothing wrong in using this term.It simply means 'the one who sits on his shaikh,s place' after he is no more.Is there any shari objection to it?The objection would be if someone says this or that person has been entitled as khalifatul muslimeen,which is not the case here.And one brother pointed out very rightly that we are all khulufa of Allah swt on this earth through Adam A.S.(though most of us don,t even own a house of our own).
Every art or science has its own terminology.You doctors are called "maseeha", does it make you one?.Is every doctor really a 'christ-lke figure'?( i would say,in most cases they remind us of Pharoa and Qaroon rather than christ.)We get master,s degree in different subjects,do we really become masters?masters with no servants in most cases,may be !
Look at the real meaning brother,not just the term used.In reality no sufi khalifa think of himself as a khalifa in the sense you take it.It is a superficial objection coming from a learned person,the only reason i can think of is TA'ASSUB,which is known for sitting on neurons and blocking all logical thinking.