I'd be shocked if this weren't a DL or VS route.

According to the 2011 Brookings data (http://www.brookings.edu/research/interactives/aviation), there were 152,350 passengers heading to London from Philadelphia. If Delta could get even 1/3 of that, which is about 150 per day, add a few odd connections and picking up another 50 passengers from UK point of sale, they could absolutely make it work as a point-to-point. Also worth noting, London is the second-largest international destination from Philly, so there's plenty of opportunity.

Expect them to announce this soon, the question is whether it will be flown on VS metal or DL metal. DL may have their smaller planes working in favor of them operating the route.