If it's on a 777 (or 763 if they are flown on the route) I'd say your chances are pretty good, and definitely worth the upgrade to sit in C over E+ (typically ~40 seats in C on the worldwide configurations, give or take). If it's a 757, your chances are still decent with 24 F seats, but the seat is not as nice.

If it's a 320 or 319, your chances go down. That said, when I was a 2P I had pretty good luck on upgrades going to/from DEN.