It's incorrect to tell children that they are in the most danger from strangers. Statistically, that is not true. Children are most likely to be victimized by people who know them well. Children need to learn what abuse is, and that they need to report it, even if the perpetrator is someone that they know.
They should keep the "Stranger Danger" message because there are more sick strangers and sex offenders out there in the world now than there was 30 years ago. Stranger should still mean danger. Just because many children know their abusers does not mean that strangers don't still abuse little kids.
Yes, the phrase, "Stranger Danger" leaves many children at risk of abuse. Statistically, only a small percent of child sex abuse cases involve total strangers, whereas most cases are committed by adults who are in some way related to family. Still, it is my opinion that the phrase it helpful to keep children aware of their surroundings.
"Stranger Danger" can be misleading, since most victims of abuse suffer at the hands of people they know who have the opportunity to win and abuse their trust; in other words , the harm doesn't come from strangers. Teaching children to automatically distrust people they don't know doesn't keep them from harm. It's not bad to teach them to be cautions, especially if a stranger asks them to get in car or go somewhere with them, but there are other things in addition to strangers to focus on in teaching children to avoid situations which can lead to abuse.