Virgin Atlantic are part owned by Delta, and have recently been taking over a number of Delta operated flights from Manchester. If we see Virgin operating from EDI, then it will be at the expense of Delta, rather than an additional route.
A second Chinese route is a possibility - a rival carrier may choose to step in to the market before Hianan gets too established, however with GLA recently signing the agreement with Shanghai, I think the next Chinese route will be more likely to go to GLA than EDI.
Other than that, I can't see much long haul on the immediate horizon. Possibly a return of JAL charters.