a new terminal is being developed at Bijwasan which is within 5km range of GGN, so no need of quadruple...
and Yes , there is immediate need of 3rd line between RE-GGN , even fourth line is required (2 for DLI-JP and 2 for DLI-BKN/RGS-AII/HSR)
and good thing is that Railway has already sufficient land for 3rd and 4th line between RE-GGN