Finally got around to watching the finale, and I thought it was pretty good. Something of a let down from some of the great early episodes of the second half, but a cool way to terrorize Rick's group. My take was that the Saviors have been watching Alexandria for a long time. They knew about the spiked cars in the front, so they've obviously gotten in close. We know they have patrols and contact over the airways from when Maggie and Carol were captured. I think they planned out those barricades way in advance, then put things into motion and improvised as needed. They probably knew when Daryl left and a small group followed, and they likewise probably called it in when the RV left. I'm guessing they made the connection to the Hilltop as well, so easy enough to figure out which roads to block and shift teams around between the two sites. They probably had scouts all around the woods and called it in when they started unloading the RV too.
The Carol leaving thing is very irritating. I wish Morgan had just convinced her to return somehow or she had died.
I'm among the few that really didn't mind the cliffhanger. It will spur lots of guessing and discussion, and they'll get a large crowd for the S7 premiere to find out who it was. If they kill a big name like Daryl, you might have some people get pissed and leave the show. If you kill a bit character like Rosita or Sasha, it's not a meaningful loss and people complain that the writers chickened out. They are much better off making us wonder what happened.
I do think it might have been Glenn just given all the recent goodbyes with Maggie. But I think Negan understands the value of keeping loved ones around to make sure you have something to lose/fear. Given that, I think Maggie/Glenn and Rick/Carl are both safe. In the comic, he jokes about not killing the minorities because he doesn't want to play the race card, so that could mean Michonne, Sasha, Rosita, and Glenn are safe too. I'm guessing it's Eugene or Abraham. They had a little make up session beforehand and either looks big enough to have a better chance of surviving that initial hit from Lucille. Eugene gave the bullet-making info to Rick, so the story doesn't need him for anything else. And Abraham has been acting weird for a few episodes now. He would have been dead by now anyway in the comic-verse. Runner up guess is Norman Reedus for the reasons above and I think Negan would see Daryl as someone who might stuggle to fall in line.
Its gonna be a long wait to find out....