I'm sure it's a new group.
Rick smiled at the end, and I think I know why....... these are rough & ready survivors he's found, and they do NOT seem to be Saviors, and he's looking for numbers to help defeat the Saviors, and they didn't kill him on sight, so he's thinking he might have a 50/50 shot at being able to join forces.
At this point, he and Michonne both are becoming convinced that their group is like "the chosen ones" (or something to that effect) such that no matter what happens, the majority of their group for the most part is going to be okay and win in the end. There's a bit of overconfidence going on, but even so, it's giving them a sharper edge that they didn't have before. Stop being the victim and assimilate some of the Saviors badassitude... but not so much as to turn into complete bad guys like the Saviors. He smiled because he figures the odds are decent that he will be able to convince these new folks that they need to be friends and help each other out. Maybe not today or tomorrow, but maybe later. And whatever it is that they might do to Rick or the Alexandrians, it cannot possibly be any worse than the Saviors. So, he almost finds it funny or entertaining to see what's going to happen next.
As do I. I don't know about the rest of you, but I am totally fired up for the latter half of this season!!!