Here is the lead of Airbus’ press release:
India’s largest low-cost carrier, IndiGo has signed a Memorandum of Understanding for 180 eco-efficient Airbus A320 aircraft of which 150 will be A320neo’s and 30 will be A320s. It is the largest single firm order number for large jets in commercial aviation history, and also makes IndiGo a launch customer for the A320neo. Engine selection will be announced by the airline at a later date.
While the press release says engine selection will be announced by the airline at a later date, the graphic provided by Airbus has the PW Geared Turbo Fan version, as opposed to the CFM LEAP-X, illustrated.
We don’t know if the PW engine illustration means anything in terms of engine selection, since obviously Airbus had to select one version (PW or CFM) to work up. But this is intriguing.