Inter still have several difficult games ahead, so Napoli will have a chance.
With current position, i think the chance for Napoli is a bit difficult. I know Inter just 3 point ahead Napoli, but if Napoli also made another mistake, 3 point will become more far away. Even inter have another big match with another competition schedule, they will start to keep their points gap with Napoli still save. Just few match away, very possible to secured their position.
But it works the other way around too - if Inter loses 3 points, Napoli will be level with them and there will be no more room for error. Inter's problem is that they have a super tough game with Bayern and then (if they are lucky with Bayern, which is very likely) two games with Barcelona. I think with this setup it will be impossible to show equally well in Serie A and the Champions League. Napoli have no such problems and are waiting for their chance.