If you don’t know what I mean, it’s the mission before the final confrontation with Dutch and when their vehicle crash, Ross is then killed when it crashes. So, imagine what would happen then.
But Edgar Ross was the one that had the idea to send John to hunt his gang members. Plus he was the one that found him. So if John Marston heard that there were hunting his gang embers (he would be harder to find since he wasnt doing any criminal activities, unlike Javier or Bill) he would´ve time to sell the ranch and move to his family. The ranch maybe had made enough profit to leave the country (To Canada or even.... TAHITI)
If Ross was killed, Dutch would still be hunted down by John. John wouldn't die later, as Fordham would be promoted to Ross' position, and Fordham had respect for John unlike Ross.