I think it's harsh on Evans to be dropped. When you consider how long M-Sport persevered with Matthew 'Sunday driver' Wilson (although there might have been other reasons for that!!). He did quite well last season - he was steady and solid in most rallies but also went for it when he had the experience/confidence on events to do so; see his second place in Corsica and a string of powerstage points. He obviously has ability. Maybe not likely to be the next British WRC champion, but he did well.
I just think M-Sport are absolutely desperate for the 'magic driver' who will get them a win. Neuville couldn't despite finishing second in the points, then they hired Hirvonen who couldn't return them to the top step, then pinned their hopes on two youngsters who in Evans' case was solid and did everything that could reasonably have been expected, but not enough. They'll see Ostberg as a safe pair of hands and Camili as the wildcard.