Gul's interview was good because it gave an insight into the characters as they were perceived and have been portrayed so far. I'm certainly glad they changed the 2 working titles and finally named it IPKKND. This definitely means the crux of the story is the unconventional love story of ARHI.
Plus if you go by just the interview, Khushi seems to have the least importance but in reality she plays the strongest character and her screen time is maximum probably even slightly more than Arnav's. Thus i believe that the bro-sister angle will come into play where he chooses Anj over Khushi but i do think when the truth is out Arnav WILL support Khushi. It will be Khushi who will make Arnav chose Anj, because she knows her importance in his life. This may lead to a brief separation track where both realize they cannot live without the other😃
Also a lot of importance has been give to DM in this serial, the engagement, wedding, post marriage rituals have happened with DM's blessings and we know DM can never really cause long term harm to Khushi. If the whole bro-sis angle were to gain focus, that would mean doom time for Khushi and looking at how the CV's have maintained the DM angle, i don't think that will happen.