I think if the PS4 NEO launched this year its a big mistake on Sony's part and they could potentially find themselves with the weakest spec console by 2017 depending on what specs the NX launches with and Microsoft deciding to go for a 4 year trigger to start a Xbox Two for holiday 2017 release. PS4 NEO isn't needed and they would sell the same amount of console this year if it launches or not and if anything it could be a negative and cause themselves some bad PR and unhappy early adopters.
NX as new hardware will always be more relevant than a new upgrade model.