They are going to be a big part of the future, yes. The only problem is that they take a lot of time and money to do well.
Fallout 3/NV are the pinnacle, for me. So many things to do, places to go, stuff to find. On the other hand, I'm playing Far Cry 3 right now and I'm sick to death of tigers and jungle. The story is good but it's lacking in variety. That's a big challenge for open-world games, especially realistic ones.
As far as JRPGs go, most are quite linear, though they often fool people into thinking they are not. It kind of amuses me when people bash FF XIII for that when many others JRPGs, like FF VII, were much the same.
Linear games definitely have their place. Open world games can be fantastic but they can also be boring. If a developer can't do an open world game justice then they should probably look into making it a more controlled experience.
Now, that being said, Fallout 4 is my most anticipated game. It should be glorious.
