here's how it ended up: I switched from original (11:20am) to the earlier flight (9:35am) flight since neither had departed. Gate agent at earlier flight said "you should switch; this one will definitely go earlier than the 11:20." So I switched. At about 11:30, the original starts boarding; the earlier says "we'll get an update in a half hour." Walked over to original, which is now almost fully boarded. Ask the GA if I can get on; he says my original seats are gone but they have one left. GA says "you shold definitely take it; we've got a plane and a crew and we're boarding." But I'm with my wife and there is only one seat. Original pulls away from gate. Back to earlier gate, where they make an announcement that their departure time is now after 2pm. Damn! Mrs. W gives me the "you think you're so smart" look. Back to the AC to wait it out.
After an hour or so, people start streaming into the AC from the original (11:20) flight. They had pulled back to the gate and deplaned. That flight was straight cancelled. I've got confirmed seats on the earlier flight, which eventually departed at about 3:15.
Bottom line: switching proved to be the right move; otherwise I wouldn't have gotten home til next day. However, it was just random luck and for a while looked like the wrong move.
Oh, and btw, I do actually have a crystal ball, but neglected to bring it on this trip.,