People involved in the program. You can also do a google search. Airbus has been counting on a major far east order which has not come in part because of the performance issues. It burns more gas short haul then the CEO version due to the weight increase. I also did not say it won't be built, I stated it might not go into production. Depends on the status of existing orders and new orders. Currently there are only 120 orders give to take that are considered solid and 175 total.
Here is the big issue:
Perhaps more interesting at this first analysis is the decline in fuel efficiency gain when shorter ranges are flown. We have a decline of 20%-30% from 4,000nm to 1,000nm. We can thereby conclude that Kiran Rao, Airbus EVP of Strategy and Marketing, meant something else with the quote “for 2-3 hour missions, the A330ceos are still more efficient than a neo,” (from this discussion with Aviation Week).