[tewall]

I don't think so about the river. Without a read, I would call without thinking.

A pot bet at the river gives you 2 to 1 odds to call, meaning you should call if your opponent will bet a missed hand once for every twice he has a made hand. If your opponent takes a free card on the turn, that means he's drawing. He's only going to hit that draw around 1 in 4 or 5 times (maybe somewhat more if he has multiple draws). For the time being, let's say it's 1 in 4.

So the 3 out of 4 times he misses, what will he do? In order for your calling him to be wrong, he would have to not bet when he misses 5 out of 6 times. (this way, he's betting twice with the goods, and once without them, the correct ratio to make it immaterial whether you call or not). Very few players have that much patience. They will bet more than 1 out of 6 times when they miss, so you can safely call.

You don't even care what the river card brings. Just how likely he would be to bluff vs. making his draw. I think the clear majority of players will bluff enough to make calling the right play, but if you were unsure you could resort to game theory, which would suggest calling half the time to a pot bet at the end.