GW2 won't have to "perform" like a traditional sub-based MMO, as it's B2P as you said. But GW1 had about 3 million unique users or something (7 million total sales iirc, but that includes all expansion packs), GW2 could end up around there with ease I think if it delivers.
NCSoft buying EA doesn't seem unlikely though, EA has a handful of powerful franchises but the company as a whole isn't very strong is it? Stock has been in a downward spiral for years now.