The person being beaten will die. The show has gone out of it's way to impress upon the viewers this season that Neagan ALWAYS kills a member of a group as an example to the others. Even his road gangs have the same standing order as we witnessed with the original Daryl/Sasha/Abraham run in with one. I'm pretty sure the pictures the group found on the wall of the Savior collection station (the ones of bodies with their heads smashed in) were of Neagan's previous "examples". Someone is most certainly going to die from the beating, the question is who.
My theory on why they chose to end in such an unexpected and frankly lame fashion is that all season long they've been telling viewers that "Neagan's entrance on the show is going to be the same as in the comics!", which has resulted in comic readers pretty much spoiling who was going to die in many threads and articles across the internet. By ending it this way, they can claim that Neagan's "entrance" was exactly the same as the comics, but they can then switch his choice of victim because it won't be revealed until S7E1. That is just the sort of stupid Magic Dumpster misdirection that TWD's writers seem to get off on.
After thinking about it for awhile, it is plausible that Neagan's crew had a spotter near Alexandria who radioed back that the RV was on the move. They also probably figured out by now that Hilltop and Alexandria had an alliance, or at least that Hilltop was supplying them with food. So they surmised that at some point Alexandrians would want to head to Hilltop, and setup the elaborate series of roadblocks and detours to force whomever attempted to make the trip into their trap. It's a stretch, but given the sheer number of Saviors and the fact that they are well equipped and have radio communication, it's not exactly as magical as it appeared in the episode.
That said, by the second roadblock it should have become VERY apparent to Rick and Co. that the Saviors were on to them. At that point it becomes obvious that the Saviors are trying to prevent Alexandrians from reaching Hilltop, and the next very simple logical conclusion is that the Saviors have also compromised Hilltop again. I mean seriously, Rick sees all this effort the Saviors have gone to, and he doesn't once think that even if they reach Hilltop, Hilltop isn't going to be there anymore, or is going to be overrun by the Saviors making the trip moot. At the second roadblock, and surely by the Red Rover one where it was obvious the Saviors were not trying to kill them (and thus were leading them into a trap), the decision should have been made to turn around and head back to Alexandria despite Maggie's condition. Once again, TWD has smart survivors make stupid decisions because it's convenient for the plot.