Yes, I've read all of the books once and working on finishing them for a second time. The show is VERY different than the books, so nothing in the books that is made clear means anything for the show, obviously.
Yes, there were white walkers before, but if you read the books you would know that the night king was the first white walker created by the children of the forest and he never died previously. So sure, the walkers can come back if the children of the forest decide to make the same mistake twice... it's also obvious that that won't happen because they know now that it was a bad idea and it created a monster.
So the night king (first walker) dies and all of the other white walkers die as well. So there's no reason to assume at all that they would come back. Sure they may have a night's watch but I'm pretty sure it would make more sense for them to only create it if needed as it's a massive waste of people and resources to keep it active when all of the white walkers are now dead. See where I'm going?
"Wildlings aren't a people that historically like to be ruled"
True, except Mance is literally named "The King Beyond the Wall". And by reading the books or even just watching the show you can see that he has power North of the Wall and directs people to do things. He is fair, so there aren't really any issues and they aren't a conflicted people so there aren't battles over power really, just feuds between clans occasionally, he is still regarded as king beyond the wall. Mance is dead, Jon goes North, so one could assume that he may become the next king beyond the wall. So yes, there is evidence to show that this is a possibility... much more so than guessing that Jon is now part of the Night's Watch and is just escorting a bunch of wildlings into the forest then returning South. Right? You have to be able to see that even if you haven't read the books. It's just obvious the way the show made it, but you can think differently and that's fine because we will never know exactly what happens after the last episode.