In the end of issue 99 one of the Saviors says "We attack at dawn". He obviously meant attack on Alexandria and not group heading to Hilltop. Considering issue 100 happend during night and ended during sunrise, Rick and others won't be able to get back to Alexandria at time. But on the other hand Negan already stated after Glenn's murder that they will come for their first offering in week so he probably considers Rick's group as punished enough. I would just like to hear your opinion about this.