Guesses:
EWR: Seasonal summer service to 2/3 of the following: CPH, OSL, VIE, HEL, MGA, WAW, HAM, DUS, BUD, NCE, OTP, STR, BSL, or DBV. If they're really feeling ambitious, a year round flight to either TPE, ICN, BLR, HYD, CCU, or MAA.
ORD: Seasonal BCN or KEF service seems plausible, although TLV has been long rumored as well.
SFO: Given the announcement date, anything South Pacific seems unlikely. Elsewhere in Asia, I don't see anything in China and PUS/MNL/BKK/SGN/HAN are possibilities but unlikely. Seasonal BRU or DUB perhaps?
DEN: The airport really wants a China flight and is offering incentives, so perhaps PVG. However, given the recent European success, I could see LHR going year round or a seasonal CDG flight.