Well, I would roll random chance for another gnoll patrol showing up (if group was deep in gnoll territory or gnoll stronghold or such). Not default that automatically another pack shows up (and also there is chance other monster may show up as usual with dungeons). But if gnolls were raiding party, then it would definitely be win for the group (more so familiar can use potions; take master's potion and uncork and pour potion down master's mouth to cure him/her).