Unless the Dodgers collapse, the field for this year's WS is already determined from the NL. However, upsets do occur. The 1973 NLCS comes to my mind.
I wouldn't count out the Braves.
As for the Cubs, it would be nice to sneak in but they don't have what it takes to make the WS and they have too many injuries. I'm more interested in what off-season moves they make to become a contender again/replenish the system/retool on the go.