This wasn't really that big of a surprise. The development cycle indicated that it would most likely come out this September. Their page also says it will stop giving a 5-year warranty for FairPhone 4 starting with September.
With that said, I'd give this one a go if it was more secure. However, until Graphene OS doesn't tip their toes into this, I'm not jumping ships yet. Would love to, though! I really like the initiative.