It will be advertised like WoT. It will get people into flying combat games, some will inevitably come to Aces High looking for something more.
This is a great point. Back in the days of Everquest, every time a competitor came out with an MMO, at first people left for the new game and subscriber numbers dipped slightly. But very quickly people came back in much larger numbers than what left. Three things happened: original players came back who didn't find a game they liked better, new players to the new game came to EQ after being told about it, and the market for MMORPGs expanded. After this happened a few times, the EQ staff publicly said they looked forward to more competition, because they became better off each time a new game came out, even when the competitor was actually good.
I expect the same thing will happen for Aces High. Of course the big cautionary tale is that when the one really good MMO came out, World of Warcraft, it didn't turn out so well for Everquest. But WoW's success was built on really great design and technical competence above and beyond what Everquest ever delivered, and the perception by gamers that Blizzard never produced a bad game. I think the only one of those that World of Warplanes could possibly do better than Aces High is design, so it looks pretty good for HTC.