Even if in future WAP12, WAP13 or any high power locomotive comes bankers will still be required. Its a simple science. Imagine u r climbing a steep incline. Force will always be from one end. And that will put more pressure on couplers holding to each other. What if in incline position the couplers break? Won't they roll back and derail which is a severe danger. I have seen even empty EMUs too with bankers climbing ghats even though they are in multiple units. Hence bankers are always safe and helps climbing ghats a lot. RDSO will never permit single loco climb at these locations.