They are just not ready.
also the neo & max news
It will be couple of years of slip. but it is just as well because some the their technology has not matured to a point where it is useful.
The reason C919 is competitive is because it can come earlier than the re-engined neo and max. by about 5 years.
but if it is going to slip anyways it might as well be a full fledge competitor.
it will be competitive as long as it is demonstrated to be safe.
It sounds like CFM is having some delays on the Leap-X as well, since they have just announced that the design has been completed, test flight of the engine won't happen until 2014, so C919 will have to be delayed, but CFM is confident of a 2016 date for the engine to be ready for commercial service.