Yea but I interpreted the cinematic a bit differently. You need to fully digest what occurred. Saurfang is an "Old Soldier" bound by traditional Orcish beliefs of honor, and the most honorable thing to do is to die in battle. If you re-watch the Alliance version of his son's death scene in ICC, you see that he greatly appreciates the Alliance granting him access to his dead son to give him a proper burial. The Alliance king calls his son a hero, and Saurfang addresses the Alliance king as "Highness". Saurfang acknowledges the sense of honor within the Alliance, and so he clearly would object to what Sylvannas is doing. Furthermore, the young Troll (who had a father that died fighting alongside Saurfang) probably made Saurfang realize that for a lot of the individuals in the Horde, the Horde is all they have. This was enough to make Saurfang turn around, this may be enough to make Saurfang strive to make the Horde a better place, whether he lives or dies. The way the story is shaping, it really does seem that a Garrosh 2.0 is going to take place.